My best non-running sports achievements aren't very high-level, but they were a lot of fun.
I beat the whole starting five of my DII school's basketball team in consecutive 1-on-1 games (to 11, winner's outs, win by 2) while a 6'1", 155-pound sophomore on the cross-country team. And after two guys had lost, they were on to most of my tricks. The last game was against a 6'8" forward who I tired out by running all over the place, shooting from outside, and sprinting after my own rebounds if I missed. The final game went to something like 13-13, I went up by one, and then I made a left-hand hook that I'd saved throughout all five games so I could surprise someone with it.
I had a similar victory over a 280-pound shot-discus guy: In a fitness class taught by the school's water-polo coach, we'd learned that to bench-press 100 pounds as many times as possible in one minute, the best way is to start slowly and keep a steady rate of about one lift per second. I did 60 with that method after doing about 33 while starting really fast--which makes you go totally anaerobic at less than 30 seconds, after which you're reduced to long pathetic gasping waits between lifts for the last 30 seconds. Armed with this knowledge, I challenged the biggest guy on our track team to a bench-press contest in front of about half the team while we were in the weight room. Of course he thought I was joking; he could bench over 400 pounds. I gave him the rules and "allowed" him to go first. He blasted out of the blocks, so to speak, and had about 40 lifts at 30 seconds. He was then completely exhausted and got 15 or so in the last 30 seconds. I acted very impressed, really milked the prelude to my turn--and then did 60 without much trouble, to the huge delight of the audience, both distance guys and weight men. The thrower blustered and scoffed and kept saying "Let's go for max!!" But of course I wouldn't let that happen.