Ax-Crazy pirate queen Bangladesh Dupree is tasked with guard duty and told to kill anyone who enters the room unauthorized. She asks if she is allowed to use any weapon she wants; the list includes cheese.
That one's not to hard to figure out; you just ram the cheese down the person's throat until they choke.
Lots of this pops up during the battle with DMK too. Cinderblocks, stone busts, crates and barrels, candy, and even two time-traveling versions ofPickle Inspector are used as weapons. It's safe to say that MS Paint Adventures practically runs on this trope and Mundane Made Awesome.
Also from Homestuck, Mr. Egbert's weapons of choise are cakes and SHAVING CREAM.
Bro rivals Mr. Egbert up there, by using Lil' Cal in his fight against Dave. He also knows the art of "weaponizing a sylladex", by loading it with heavy items to be expelled as projectile weaponry when needed.
Grape Jelly of Housepets! is fond of wielding a broom as a weapon, which she first did to ward off a pair of raccoons who had broken into her kitchen. Tame enough, right? But later on in the comic it's revealed that she once did the same thing to beat the crap out of a kidnapper and his pet alligator. And he was an armed kidnapper. And she was still a kitten at the time!. Though she didn't actually do it, Grape has also threatened to suck down the end of a candy cane and shank someone with it.
In Questionable Content when Martin and Steve are attacked by the vigilante Vespavenger they defend themselves with what's on hand, a stop sign and a trash can lid. Lampshades JRPGs when Martin comments,"I am nowhere near effeminate or spiky haired enough for this.
The stop sign makes a reappearance, along with a broom, when Martin, Faye, and Dora confront the Vespavenger.
Schlock of Schlock Mercenary once used a lump of battleship plate against an enemy, fulfilling both this trope and Shield Bash (which is what said plate had been used for until then). Schlock himself is an improbable weapon.
Tailor as well, who uses his scissors as terrifyingly effective weapons. As he does have to cut through the local super-resistant clothing, he can snip off a super soldier's hand with little trouble.
Mike of Mike Bookseller has a tendency to use spatulas as weapons when sufficiently angered.
Dame Madeline Goodlaw from Rusty and Co. seems to have the ability to turn random farm implements into powerful magical weapons. So far, she's turned a hoe into a Holy Avenger, a shovel into a Vorpal halberd, and a pitchfork into a Trident Of Warning.