Shit, what didn't I try when I was a kid, or even older? Basically EVERYONE'S finisher, and trademarks like chokeslams, Scott Hall's fallaway slam, Rock's spinebuster, etc. I also loved applying submissions, and I take pride in knowing how to correctly apply Bret's version of the Sharpshooter better than any WWE wrestler who ever tried it.
One time I took a Stunner in my friend's living room, and he landed foot-flat on the floor, causing his knee to point straight up and I bashed my nose right into it. Blood everywhere. Sadly, I no-sold it and ran straight to the bathroom.
Another time I was wrestling my younger brother in the basement and we laid out couch cushions on the floor, since the carpet was stupidly thin and it was cold, hard cement underneath. At one point I was beating the shit out of a large teddy bear he had, and I suplexed it on what I THOUGHT was the cushions. Ended up smacking my head on the thin carpet and saw little grey stars for a few moments. That fucking hurt.
A group of friends and I in our small town also used to get together at the park after school and have "Royal Rumbles". There was a gazebo-type structure shaped like a square, and we eliminated each other by dumping opponents over the wooden railing. It was maybe a 3-foot drop at best.
One time during a Rumble, a buddy of mine had set up a broken piece of fence and stood it in the corner. On a complete whim, I let him reverse an Irish whip and I plunged myself through it like Mick Foley in 1998. It was weak wood so it really didn't hurt, but it was an awesome bump. Everyone started a Holy Shit chant and I let myself be eliminated once again.
I think the funniest thing about backyard wrestling when I was a kid was my buddy Rory's amazing enthusiasm for it. He went so far as to dress himself up as his favorites. One time he arrived wearing green shorts that had constructed sets of fake lips and the name Mr. Ass written on the back, but the best was when he made a spectacular entrance as The Rock, complete with trunks, elbow pad (only to throw it away per People's Elbow), and paper sideburns from when Rock had them in 1998/99.
Shit, those were fun times!