Awesome but Impractical/Web Comics

"A flashy feature that has limited usability for victory."

Riff uses one of these in this Sluggy Freelance strip. At first a gatling gun that fires 100 stakes per second sounds like a great anti-vampire weapon. But when you realize that it can only hold one hundred stakes at a time and takes two days to load ... well, you can stake one vampire really, really good. The other dozen or so will tear you to pieces.
- He eventually makes it better by adding a beltloader, similar to a mini-gun.
- Most of Riff's inventions (at least in the earlier days of the strip) seem to fall into this problem. Look at some of the later (and alternate universe), stuff, however...
The pair of wings Buwaro gets from his dead sister's pendent in Slightly Damned look REALLY cool, but are too small to fly.
Eight Bit Theater: "Sword-Chucks, yo!"
- Sword-Chucks were only recognized as unusable by every idiot in the cast. White Mage pointed out they could be useful with a longer chain.
- Staff-Chucks: Like sword-chucks, except that they shoot magic in every direction. Black Mage loved them, since destroying everything in sight is his favorite thing to do.
Order of the Stick's Vaarsuvius has chosen to specialise in evocation magic at the expense of conjuration and necromancy. In layman's terms, this means s/he has access to a lot of flashy destruction spells at the expense of losing access to many 'utility-effect' spells (teleport, summoning minions, level drain, etc). Many experienced D&D players are of the opinion that damage-dealing evocations are one of the least optimum ways of utilising a wizard's power. Tthe method used to counteract this temporarily--the Soul Splice--wasn't much better. seeing as it involved RENTING HER SOUL (trust me, it makes sense in context and only lasted so long, as well as making him/her feel sufficiently omnipotent to take on Xykon and the rest of Team Evil...single-handedly. In short, once is enough.
The Adventures of Dr. McNinja has Chainsaw Nunchucks. Badass, but no human being could possibly wield them. That's why they have the Uberninja though.
- Also Frans Rayner's laser eye. Highly destructive...but burns calories to fire, tiring the user out in one shot.
Nedroid: Reginald has two of the world's deadliest weapons: invisible swords.
Irregular Webcomic has a laser-nunchaku and the quadruple, quintuple, and septuple laser swords.
Deconstructed in this Subnormality strip
Taken to hilarious extremes in Oglaf with a weapon the dwarves make. NSFW
When Jade enters the medium in Homestuck, Bec prototypes her kernelsprite with himself. The upside? Jades sprite is a Nigh Invulnerable Reality Warper! The downside? So are all the mooks...
- The Unreal Air gives you unlimited vertical flight. Stable, blandly slow, unsteerable flight. Dave finds a good enough use for it to ascend to his Gates, but it has no other practical use.
A Loonatics Tale: Lynch Cruor fights using a Punjab lasso; in layman's terms, a weaponized hangman's noose. Unfortunately, he's a vampire who's just shy of 1000 years old, so he's had plenty of time to practice.
Yehuda Moon and The Kickstand Cyclery has Arboritum, an extremely light alloy that would be excellent for bikes if it wasn't also extremely fragile, ensuring the rider serious injury from frame cracking.
In Misfile, Vashiel is an angel of punishment, so he gets a Big Fucking Sword that flames and can smite evildoers in a second. His brother, Rumisiel, is a filer, so he gets a multi-filing tool, with a recorder, web access, and other Boring but Practical things like that. Guess which one comes in handy?
In Collar 6 everyone appears to go through their life dressed in BDSM attire.
Swords got Sickle, who usually gets carried away and designs such things at best (and simply impractical ones at worst). Like that impressive three-handed sword. Having foreign objects stuck in her head may have something to do with this.

Sickle: Welcome to Clayless Industries, where we make swords nobody can use!