Happens from time to time in Survival of the Fittest, especially when students who are assigned useless weapons simply make new ones out of available materials, such as Niniko Kishinawa (v1) and Dan Brent (v3) making spears out of nearby items and, in Niniko's case, a shaft of bamboo. Walter Smith of v2 also used his assigned rock to smash a window and make a knife out of the biggest, sharpest, fragment he could find. To top it off, Dominica Shapiro killed Nigel Gillespie with a frigging ocarina, while Blake Ross killed Gregory Moyer by hitting him in the face with a bible and knocking his head onto a rusty nail. And lets not forget the most recent case where Shameeca Mitchell killed Boxer Carvahlo with a customised double-ended dildo!!.
Less immediately fatal, no less impressive, V4 example, combined with Product Placement: Jimmy Brennan and the can of Moxie.
KateModern often features Improvised Weapons, such as Terrence's garden gnome in "Seven Dials: 5pm - 23rd November 2007" or Lauren's cricket bat in "Batwoman". At one point in The Last Work, Charlie uses an ornamental sword that just happens to be on hand.
Chaka, in the Whateley Universe, has control of Ki, so her aim is unnatural. She disarms a sword-wielding super-powered ninja using a handful of playing cards. And then there's her aim with a sewing needle...
She's been known to shelve books by throwing them just right without getting up. This tells us everything about her ki-powered Improbable Aiming Skills that we'll likely ever need to know.
During the battle at Lab 101 Alfred throws a boulder at a Dragonstorm experiment.
During said battle, Alfred also uses a sledgehammer to behead another Dragonstorm experiment.
Again during said battle, he throws an oil drum at a Chimera. It is not very effective. Then follows it up with a pickax. It too is not very effective.
Aimee uses a broken pickax handle to kill one of the Lab 101 guards shooting at Alfred.
Alfred kills the remaining Lab 101 guard with a log.
Gustave subdues Slash with a tool box then a mechanic's cart.
Shelton subdues and then kills someone with a pot of boiling coffee and the coffee maker.
Gustave's use of a handicapped parking sign as a club probably counts.
Sharon uses a hammer intended for breaking the glass on a box containing a fire ax to kill a guard.
Dr. Zanasiu uses a fire extinguisher as an impromptu smokescreen to get past a group of guards. He also uses it to bludgeon a guard.
When Famine turns everyone on each other, Zachary and Gustave proceed to try and kill each other with a variety of improvised weapons. Zachary with a welding torch and then a fire ax. Guistave uses a filing cabinet and then Zachary's dropped ax.
Dr. Kerzach sprays lubricant into an assailant's face.
A rogue worker attacks Dr. Kerzach with a fire axe.
Rhino throws a motorcycle at Subject 18.
Ruby Quest has a few of these: Ace's harpoon, Ruby's heavy gloves wrapped in barbed wire, and the BLUDGEONY CANESHOVEL.
Unlikely Eden manages to make an axe one of these - as wielded by a ten year old girl.