ECW employed this frequently, with everything from "Singapore canes" to fire extinguishers, staple guns, stop signs, barbed wire, and, on one occasion, a Sega Genesis. The style was later aped by WWF and WCW, with their hardcore matches; they added implements like galvanized-steel trash cans and cookie sheets to the mix. One infamous hardcore match between The Rock and Mankind saw Rock pummel Mankind with the handset to a pay phone while screaming, "It's for you!"
The original ECW Arena was located near a thrift shop, and for a while, the management held contests for the most original fan-brought foreign object — not only the above, but a laptop, a plastic lawn-santa, a hobby horse, a Nintendo Entertainment System, etc. (This undoubtedly made the thrift-shop owners happy.) Unfortunately, one fan didn't really get kayfabe... Foley said that he had become accustomed to swinging cheap aluminum pots and pans, then got handed a cast-iron skillet and didn't realize it until mid-swing. His opponent, The Sandman, ended up with a concussion that kept him out of action for two weeks. This brought an end to the fan-brought foreign object contests.
Speaking of skillets, that was how "Mighty" Molly became one of the few women to win the Hardcore Title, by defeating her mentor, The Hurricane (she lost it shortly after when she ran into the upper half of a door that Christian was opening. He looked guilty at first, but then pinned her to claim it anyway.)
Mick Foley mentions in his autobiography Have a Nice Day that the best improvised weapon he used was... a two-man kayak. Which just goes to show that you canhave your kayak and beat it. He also mentioned a match against Owen Hart where they attacked each other with giant bags of popcorn. POPPED popcorn. It was mostly intended as a joke.
One memorable match in SyFy's ECW had Tommy Dreamer ram Christian into a hotdog cart and start hitting him with the contents inside, taking a break to eat. Christian came back and finished him off with a car door.
Most "traditional" wrestling weapons are improvised, anyway. The ubiquitous folding steel chair is one of them — jostle someone sitting at ringside, fold, swing. Need something hard and heavy during your title fight? You earned a title shot— go grab the belt and give one to your opponent! The guy with the microphone talking too much? Hit him with it! It's actually rare when a real 'weapon' is ringside, although some performers do have their trademark items. Chains show up from time to time, as do brass knuckles and kendo sticks.
Chris Jericho pulled off one of the rings on the ropes used to lift the steel cage and then beat Batista bloody with it. He also once knocked Chyna unconscious with a hair dryer. Why he happened to have a hair dryer is a mystery for another time.
There's always some "random" stuff under the ring, ostensibly left there by the crew who set things up in the arena that night. Jim Ross once lampshaded the hell out of this:
J.R.: "If I live to be 100, I will never understand why they keep so many damn weapons under the ring. It's like they want the wrestlers to use them on each other..."
Good ol' J.R. himself managed this once, by taking a glass candy jar to Tazz's head during the latter's match with Jerry Lawler.
Expect any injured wrestler (or wrestler feigning injury) to use their cast, face protector or crutches as a weapon.
Chavo once pelted Hornswoggle with penny loafers. Theodore Long was infamous for striking with his shoe too.
When falls count anywhere, expect to see some strange things. Luna Vachon found a scanner and made several copies of Ivory, who retaliated by burning her with a clothing iron. Road Dogg went after Mankind with a dog dish. John Cena once chased Eddie Guerrero with a pushmower (what it was doing in a parking complex is anyone's guess). Cena also duct-taped Batista's legs around the ringpost in one last man standing match and choked Umaga out with a ring rope that broke during the match in another. Oh, and Kane with the car battery and jumper cables.
Stone Cold driving a beer truck into the arena and hosing down the McMahons remains a memorable Raw moment. Kurt Angle would end up giving a heel-turned Stone Cold a taste of his own medicine (with a milk truck, no less!) in a similarly memorable Raw moment.
During a Hardcore Title match between Al Snow and the Road Dogg Jesse James, which eventually saw the pair fight in the snow outside, both a box of toilet paper and a set of small potted plants were used as weapons.
In an empty arena match between Mankind and The Rock, the finish saw Mankind pinning a still very much conscious Rock by using a forklift to keep him down.
CM Punk's Chicago Street Fight for the WWE title against Chris Jericho involved him breaking out of the Walls of Jericho using a fire extinguisher.
CM Punk hid amongst Raw filming crew and bashed Brock Lesnar with a camera while Paul Heyman was cutting a promo about how brilliant Brock was.
Sting and Abyss used tombstones and candelabras as makeshift weapons in the infamous Dead Rites match. There was some apparent miscommunication, as Abyss was struggling to lift the tombstones while Sting swung them with ease, even though Sting is just a guy with face paint and Abyss is supposed to be a Wrestling Monster.
Shark Boy and Curryman made use of frozen fish as weapons against Team 3D.