Gun Stripping

[cocks hammer] "That felt like 25. Gotta be able to do a .45 in 25. Did you time me?"

—Frank Slade, Scent of a Woman

This is where a character disassembles a weapon, cleans it and puts it back together. It comes in a number of varieties:

The character is undercover as an arms dealer and it's a test to see if they know their firearms by assembling a pistol. They may have to do it blindfolded.
The ability to strip and re-assemble a weapon blindfolded is regarded in Hollywood as a display of massive competence and familiarity. In real life it ain't all that difficult.
They're just cleaning their weapons.
The character is an innocent who has been trained to be a killer and this scene is when The Cutie is truly broken.
A gun nut or elite soldier may show off his skills to his peers by timing himself.

Since weapons require regular maintenance, this could be regarded as Truth in Television. Can overlap with Gun Porn. Not to be confused with a Mongolian strip-tease.

Examples of Gun Stripping include:

Anime/Manga

After being revived from a millennia-long sleep, Santana from Jojo's Bizarre Adventure picks up a gun, remarks how he's never seen a tool like this before, and takes it apart perfectly in seconds. Being a highly intelligent ancient superbeing certainly has its advantages.
Seen as part of a flashback in the first episode of Gunslinger Girl, where Henrietta spends an entire night disassembling and reassembling her pistol so that she can become familiar with how it works. Also happens at various other points with less focus.
Nearly every night in Kino's Journey.
Kazuki Fuse disassembling and cleaning his machine gun in Jin-Roh: The Wolf Brigade.
Gunsmith Cats: Obviously.
The protagonists of Noir clean their guns regularly.
Tenma does this in Monster as part of his training.
Canaan is shown cleaning her handgun several times.
Honoka from The Third the Girl With The Blue Eye collects guns and loves to take them apart.
Axel Brodie does this to his gun/Duel Disk in an episode of Yu-Gi-Oh! GX.
Riza Hawkeye of Fullmetal Alchemist cleans a blood-covered gun that was returned to her by Edward Elric.
Several characters do this in Phantom of Inferno. In fact, it was Cal quickly stripping and reassembling Reiji's rifle by instict and experimentation that tipped him off to the fact that she's actually a genius prodigy.
For Sousuke Sagara in Full Metal Panic! this is practically a hobby.

Film

Forrest Gump disassembling his rifle. And setting a new speed record in doing so.
Shoot'Em Up has a scene where Smith drops his gun into a toilet bowl and has just a few minutes to strip and dry it before a hitman bursts through the door.
Major Payne enjoys hanging upside down, blindfolded, and trying to clean his gun before his nose starts to bleed.
The comedy Johnny English features a scene where the main character, played by Rowan Atkinson, assembles a pistol. When he is done he holds it up to show, however the trigger is missing.
From The Good, the Bad and the Ugly:
- Blondie cleans his guns at one point. He has to finish before bandits enter his room.
- Tuco does this also when assembling his hybrid pistol from several others.
Ice Station Zebra. The soldiers are surprised when their Vietnam veteran platoon leader orders them to repeat a weapon stripping exercise blindfolded, even though this is a routine part of military training.
In the 1982 Ozploitation movie Turkey Shoot the female hunter is introduced assembling her Sniper Pistol blindfolded, while describing its capabilities to the other socialites taking part in Hunting the Most Dangerous Game.
In Layer Cake, Gene does this for the benefit of XXXX. He claims to do it blindfolded sometimes as a form of meditation.
In the Jackie Chan movie New Police Story, this comes up multiple times as a form of contest with one of the villains. Pretty much every time it happens it's for someones life.
This happens in Wild Target when assassin Victor Maynard is trying to teach Tony the tricks of the trade. Surprisingly Tony manages to put the gun together... but only to have it fly apart when he picks it up.
Wax in From Paris with Love can strip a gun in the hands of someone else, while it's being pointed at him. He's that good. He also bypasses customs by transporting a stripped Mrs. Jones in energy-drink cans.
Wah Sing Ku of Lethal Weapon 4, one of Jet Li's few villain roles, can also do this, as demonstrated on Riggs' Beretta in that infamous scene.
In Scent of a Woman, Lt. Col. Frank Slade demonstrates this skill for Charlies Simms. In this case, Slade doesn't have to perform his feat blindfolded because he's already completely blind.
Faster. The Nameless hitman is seeing doing this, and a deleted scene has him calling his girlfriend who is busy assembling a H&K submachine gun—a character-establishing scene for the original ending in which she is seen planning her own revenge against Driver.
Flight of the Intruder includes a scene where Tiger Cole carries on a casual conversation with Jake Grafton about why they aren't allowed to bomb the part of Hanoi where the North Vietnamese stockpile their Surface-to-Air Missiles, while he assembles a Colt M1911 that he was cleaning.

Live Action TV

In one episode of Alias, Sydney witnesses a group of young children practicing assembling a pistol. It's clearly inferred that she did something similar in her past. You see, Daddy worked for the CIA...
Jo, from Eureka, is occasionally seen timing how long this takes her.
The "cleaning their weapons" variant shows up a lot on Supernatural.
NCIS. In "Under Covers" Ziva mentions she cleans her weapon every day, even when it hasn't been fired.
In Burn Notice Fiona has to do this to prove her skills when pretending to be a kidnapper. Her response is to ask if she has to do it blindfolded.

Literature

The Bourne Identity. The doctor who rescues Bourne, having taken note of the amnesiac's old scars, gives him an automatic pistol and tells him to "break it down." Much to Bourne's surprise, he knows exactly how to do so.
A lot of Harry's friends do this, as does the protagonist himself on occasion. Justified, as their friendship with Harry often means they have to use those guns on a more regular basis than is entirely fair.
- At one point, when two Knights of the Cross and two members of the Order of St. Giles are cleaning their weapons, Harry labels them all weapon nuts, directly calling out the gun nuts and then immediately noticing the Knights cleaning their swords.

Tabletop Games

In GURPS: High-Tech the perk "Armorer's Gift" lets the character assemble or disassemble a guns in record time without even thinking. The extreme familiarity with guns helps if a weapon jams.
Warhammer 40,000: "Any Cadian who can't field-strip his own lasgun by the age of 10 was born on the wrong planet."
Feng Shui has a Gun Schtick called "Dismantle Gun" that allows gunmen to pull that Jet Li move from Lethal Weapon 4 on another guy's gun, using their Guns skill in place of Martial Arts. The Neat Freak gun schtick, which reduces the time needed to clear a jam, implies someone who does this quite regularly and otherwise knows how to take care of their guns.

Video Games

In Metal Gear Solid 3: Snake Eater, The Boss uses this as a combat tactic. She does it at about 2:46 in this video. Warning: spoilers for people who haven't played the first two hours of the game.
In Fallout: New Vegas, Caesar claims to have helped a tribe to victory by teaching them how to strip and clean guns.

Web Comics

In El Goonish Shive, Tedd likes to disassemble and reassemble his Transformation Ray Gun in order to make changes to it. Some times he forgets to zap himself back to normal first.

Western Animation

Spoofed in SpongeBob SquarePants: when Mrs. Puff is replaced by a Drill Sergeant Nasty, he asks SpongeBob to dismantle the boat and reassemble it. Somehow, he ends up with a working rocket.
An episode of |Hercules The Animated Series had Adonis, Icarus, and Hercules doing Spartan training, and part of the regime was to assemble a crossbow blindfolded.

Real Life

In boot camp, you will be given a rifle around week 3. You will not be given so much as a single bullet until three weeks later. The intervening period is spent breaking it down, reassembling it, and breaking it down again. Rinse and repeat until you're ready to shove the bolt carrier up the Master Corporal's nose.
Gun safety instructors are careful to remember their disciples they don't need to fully disassemble a gun, just separate bolt, barrel, stock for cleaning (in case of handguns: slide, barrel, mainspring) and they would better leave the more complex parts of the action like the trigger and hammer mechanism to the professional gunsmiths. They might have seen some people whose triggers went off when the gun was pointed where it shouldn't be.