Critical Encumbrance Failure

"You can't carry any more! One more item to lug around and you might just collapse in a heap of swag."

- The World Ends With You

A video game trope, similar to Wafer Thin Mint, where you can carry hundreds of kilos of equipment until you pick up one thing that puts you over the limit, either slowing you down immensely or stopping you completely.

The reasoning behind this is that if a nearly-full bag slowed you down accordingly, the slower speed wouldn't change gameplay much, but would annoy the player to no end, especially where Space Filling Paths are involved.

The weight-related version of Critical Existence Failure.

Adventure Games

 * In Quest for Glory, the game outright warns you when you're over-encumbered, which makes your character move at a snail's pace. However, one can increase the encumbrance limit by working on the hero's Strength.

First Person Shooter

 * Halo follows standard FPS procedure and limits you to two weapons, so it isn't an example, but the novel The Flood lampshades it; as the Chief is thinking choosing between a sniper rifle or a rocket launcher in addition to his assault rifle, but then reasons that “Carrying all three of them would be impractical, not to mention damned heavy.”
 * Although the game attempts to subvert this, a player could theoretically have three weapons available. However, to do this, they would have to constantly move towards their next objective, while at the same time constantly throwing away the second weapon to pick up the third weapon. Doing this repeatedly makes the player throw the current weapon forwards, while picking up the new one. So if you really want that rocket launcher to shoot at the Covenant tank in the next area, you'll have to keep throwing it forward. It's not very practical however.

MMORP Gs

 * Ragnarok Online plays it completely straight; picking up one tiny item can completely shut down all health and mana regen if it bumps you over half your maximum weight, or prevent you from attacking at all if it bumps you over 90%.
 * In Shattered Galaxy, which doesn't have random drops (being a Real Time Strategy game,) units are equipped at the Factory and sent into battle. You have to meet two Critical Encumbrance Failure limits, “Weight” and “Space,” and a “Complexity” limit that is determined by which onboard computer you give the unit (which, of course, adds to Weight).
 * Trickster Online has this, as well as an annoying 300 item limit on your inventory. Once you hit 90% weight capacity, you are reduced to walking. Reaching 300 items merely prevents picking up more items, unless they stack on a single slot, like Healing Potions. There is also a character stat made specificly to increase weight capacity.

Roguelike

 * Nethack has various levels of encumbrance, which increasingly limit your movement - burdened, strained, stressed, overtaxed (when you can't walk), and overloaded (when you can barely move your arms).
 * Same with ADOM, except when you're Overloaded! adding one more thing can crush you. Normally not a problem if you're in a safe area, but if you picked up the (self-replicating) si - *squish*.
 * Also there's a spell Strength of Atlas, which temporarily increases your carrying capacity. If a heavily-burdened hero lets the spell expire - well, he'll get Critical Encumbrance Failure and Yet Another Stupid Death in one flat package.
 * Castle of the Winds averts this trope as well; your movement speed progresses from full with a light load, about a quarter of your hard maximum carry weight, to snailpace at said maximum. It does this linearly with weight, broken only by rounding errors.
 * Furyband and ToME averts the trope. If for example you attempt to lug four Ancient Dragon corpses back to town for artifact-making (a total of 73,000 pounds) you can move, but at a glacial pace.

Mecha Game

 * Armored Core is notorious of this. Being overweight either slows your mech down like heck or it is disallowed to sortie at all. The latter is common in the first series while the former is featured in games post 2 continuity.
 * The Naval Ops series does this with ships. While increasing weight will slow a ship down a bit, go just one unit over the hull's weight limit and the ship won't work. Probably because it can't float anymore.
 * Mechwarrior prevents overweight mechs from deploying but a mech with a single Small Laser and one with a full permitted loadout both move at the same speed if the empty space in the former isn't used for a more powerful engine.

Role Playing Games

 * Most games by Bethesda
 * The Elder Scrolls series. This is amusing, but potentially fatal when you're close to the limit, and the arrow you've just been struck with puts you over and you become rooted to the spot. Made particularly obvious with the Useless Useful Spell, Burden, which artificially increases a character's encumbrance. Sadly no enemy is ever close to the tipping point so this spell only harms players.
 * Skyrim is especially notorious with this trope as, assuming an object isn't scenery, furniture, nailed to the ground or cutlery (for some strange reason ), it can be carried and will have a value.
 * The Fallout series plays this trope straight. Depending on just how much over your carry weight you are, you will either move very slowly or be completely immobile. The original Fallout had an amusing bug where your companions would only check for weight when bartering -- but not stealing or planting items. Thus, NPC followers became pack mules with an unlimited carrying capacity as the player kept planting miniguns and suits of metal armor on their person. It really sucked when they died -- how are you going to move 500 pounds of stuff now?
 * Fallout 3 and Fallout New Vegas make this even more noticeable; there's only one level of over weight (really damn slow), and it only takes a single weight unit to put you over. Carrying 280 pounds of stuff plus one empty soda bottle is apparently too difficult. To patch the obvious workaround, you also become completely unable to fast travel, so no teleporting back to your safehouse to dump your stuff there.
 * New Vegas however has a perk at lets you fast travel while Encumbrance, as well as perks that reduce weight of some of your items.
 * Geneforge plays it straight, mostly. Once you hit the encumbrance limit, you are slowly drained of AP for every weight unit over.
 * Some of the games in the Quest for Glory series slow you if you carry more than a certain amount.
 * Arcanum averts the trope with an encumbrance system that imposed penalties based on the percentage of your carrying capacity that you are using. That spare suit of armor will slow you down pretty badly even if you could carry two.
 * In Mitadake High, your movement speed will take an extremely sudden fall if the total weight of your carried items goes over 20 - even if the last thing you picked up was a piece of note paper, and you could move just fine before that.
 * An obscure hack&slash game by Westwood called Nox plays this straight as well. Bonus points for animating the character who is encumbered while running, as if he were anchored to the ground or something.
 * Ships in Space Rangers will slow down slightly as the holds are loaded, but just one excess unit of cargo will keep them from moving at all.
 * Hydlide was arguably the first console RPG series to have this starting with Hydlide 3 for the MSX and Famicom and its Genesis/Mega Drive remake, Super Hydlide.

Simulation Games

 * Dwarf Fortress has encumbrance tiers that slow creatures down for each tier crossed. Dwarves can even carry stone boxes filled with heavy metal bars on their own, but take forever to do so. This is particularly aggravating when traders turn up with a large amount of heavy objects loaded onto one of their wagons; they won't allow trading until every wagon has been unloaded at the trade depot, and in some cases they've been known to pack up and leave again before the overloaded wagon gets anywhere near.
 * In Lost in Blue, each character has a twenty-slot inventory. This leads to bizarre occasions where the characters can somehow shove twenty logs down their ass, but only be able to carry twenty leaves.

Turn Based Strategy

 * Jagged Alliance 2 subverts this trope, by increasing the "fatigue" cost of actions proportionally to the character's total carried weight. Having 134% weight means losing 34% fatigue points more than normal. However, you don't get a bonus for carrying less than 100%...
 * X-COM and UFO After Blank have something similar - soldiers who are overloaded suffer a Time Unit penalty. However, since encumbrance is a function of improvable physical strength, eventually that penalty will go away.
 * In Makai Kingdom, some equipment (such as heavy armor, large rocks and oversized weapons) reduce your movement. If it reaches 0, the unit can't move. Curiously, the reduction only takes place when you're carrying the item in an appropriate slot - carrying a boulder in your weapon slot doesn't weigh you down at all, while a merchant can carry five gatling guns with no hindrance as long as she keeps them in her equipment slots and not the weapon slot.
 * 7.62mm High Caliber averts this by providing a set limit that mercs can easily carry and gradually slowing their movement down the more they carry. However, the game's relatively realistic inventory system will generally prevent them from carrying so much that they're unable to move (trying to make them carry three rocket-propelled grenades and a backpack full of ammunition for their M60 will most certainly turn them into a slug, though). Wearing any backpack will also automatically restrict movement by preventing prone mercs from rolling side to side.

Wide Open Sandbox

 * S.T.A.L.K.E.R. plays this trope kind of straight -- your agility varies with weight, but the moment you're carrying a single gram over 50.0 kilograms you can't run for more than a very short time. At exactly 60.0 Kg you can't move at all without a powered exoskeleton.

Tabletop Games

 * Most games based from Dungeons and Dragons ruleset, such as Baldurs Gate, Icewind Dale and Planescape Torment. But not the pen-and-paper game itself, where an increasingly large load slows you down more and more, and even a load of up to 5 times your encumbrance limit can still be dragged.
 * Not that it matters, seeing as encumbrance is one of the first rules that a DM is likely to ignore for the sake of a smooth game. No-one likes to have to micromanage the weight of every single coin the party picks up, especially with the prevalence of weightless extra-dimensional storage space.
 * In GURPS progressively heavier loads make you slower and easier to hit (none, light, medium, heavy, extra-heavy). There's even one step beyond that but it costs fatigue every second.
 * In the original Heavy Gear game, the customization feature included the "load" limit, where the "load" was how heavy all the stuff you were tacking on the Gear was. The "maximum load" was determined by the Gear's parts, i.e. an Assault Gear like a Kodiak or a King Cobra would have a higher maximum load than a Scout Gear like a Cheetah or a Gila. One could approach the maximum load limit as close as they can without any consequences, but as soon as that limit is breached, even by a small amount, the top speed of the gear drops exponentially. You could have a Gear that can reach 72KPH suddenly have its speed reduced to 16KPH after you bolt on that machine gun. The manual also states that if the load exceeds the maximum by a substantial amount, the Gear would also incur stress on its internal structure, which probably means more damage if the armor is penetrated.

Real Life

 * A purse or backpack only needs an additional 300g (10oz) to go from safe to carry to being heavy enough that it'll cause fairly severe back and shoulder pain after a short amount of time.
 * Not to mention being as good as a cinder brick on a chain in a bargain brawl.
 * The idiom "The straw that broke the camel's back" alludes to this, when referring to any sort of critical threshold failure.