Throw the Pin

A character pulls the pin off a grenade and proceeds to throw ... the pin, and keeps the grenade in hand. Very common in cartoons.

This one often comes about due to a misinterpretation of the instruction "pull the pin and throw".

Anime and Manga

 * Axis Powers Hetalia does this gag as Germany tries to train Italy to throw grenades. Then later, South Italy comes along and tries to throw a grenade at Germany—but fails because of this mistake. Germany ends the gag by crying out in frustration, "What's with you two?"

Comic Books
""What have you done?!" "... Hit the enemy with my cigar?""
 * A Running Gag in Mortadelo Y Filemon; Mortadelo is given a grenade, wonders about how they are used, Filemón tells him to pull the pin, count to ten and throw it, and Mortadelo ends up throwing the pin.
 * In an old comic called Croc, we see this guy lighting a bomb with his cigar and throwing something in the next panel. Then, there's an explosion and the following dialogue ensues:

Film

 * Bananas pulls this gag twice in the course of a montage. Woody Allen's character is training with the rebels, and he tries throwing a grenade. Predictably, he throws the pin, having just enough time to make an exasperated face before the grenade explodes in his hand. Later, he tries again, and successfully throws the grenade.
 * Bones (Pauly Shore) does this during grenade training in In The Army Now.

Jokes

 * Q: What do you do if a blonde throws a keyring at you? A:

Live Action TV

 * There's a variation in the obscure British sketch show The Steam Video Company, where a soldier pulls the pin on a grenade then opens a can of Coke, throws the can and puts the grenade to his mouth.
 * There's a variation in The Prisoner episode "The Girl Who Was Death"  where Number Six tampers with the bad guys' old-timey WWI-era grenades (the ones with a baton-like handle used to hurl a can-shaped charge) so the explosives ended up in the handles.
 * This gif sums it nicely.

Tabletop Games

 * Featured in old "Canonical Famous Last Words List" (the character's background precluded him from knowing to which of two parts "throw it" should refer).
 * Warhammer 40000: Ork Stikkbommaz are noted for being above average intelligence for Orks, as they know that stikkbommz are the bit you throw, not the pin...
 * Then again since the ork throwing the pin believes that the pin will explode it probably will.
 * Paranoia occasionally has grenades where the pin is the part that explodes. Hell, it probably has some where they both do, because then they're foolproof.

Video Games

 * Worms 2 demonstrates this trope quite clearly.
 * Invoked in Dawn of War when Orks say "Hold on to the pin. Throw the other part."

Web Comics

 * In the "Bloodsuckers Are Not Sexy" arc of Fafnir the Dragon, one of the vampires is an expert with grenades... only he wound up throwing the pins at Vlad the Impaler. It ends exactly how you'd expect.
 * Maxim 65 of Schlock Mercenary's "Seventy Maxims of Maximally Effective Mercenaries" is "After the toss, be the one with the pin, not the one with the grenade."

Western Animation

 * Wile E. Coyote does it at least once in the Looney Tunes cartoons.
 * Or sometimes, the pin explodes.
 * In one, he correctly drops the grenade down a cliff, but it's bounced back at him. He then drops the pin... and another grenade is bounced back at him.
 * There's a short in Animaniacs where the Warners are being put through military training, and their sergeant is instructing them about grenades, with the above line. Wakko, naturally, throws the pin.
 * Daffy Duck does it while hunting Speedy Gonzales in Speedy Ghost To Town.
 * Seen from the outside in Robot Chicken; two GIs sitting in a foxhole with a bunker in the background. One is hit on the helmet with a pin, looks at it quizzically, and a shout in Gratuitous German then the bunker explodes.
 * Subverted in Aaahh Real Monsters. Simon the Monster Hunter throws a pin at Bigfoot, has a brief Oh Crap moment, and then throws the gas grenade just in time.

Real Life

 * Some poor recruits and trainees end up doing this under stress. Thankfully, most instructors and drill sergeants are ready to save the unfortunate newbie before any accidents happen.
 * Has happened, according to an entry in the Darwin Awards.
 * Hard to see exactly what happened in this training exercise, but it looks like something similar, judging from the position of the flash. Remember: the flashbang is supposed to be used on them, not on you.
 * Has happened on a few occasions, but the thrower is safe as long as they have not released the 'spoon' that prevents the grenade from charging. If the spoon is released, it is not a good day.