Gotta be 71 in 2002. A robot that can't, turn, falls on the ground at the start of every game, and can haul the entire alliance and all goals (700+ pounds) for the win. All at a slow pace of probably 2 inches/sec. Every match won in 5 measly seconds.
https://www.youtube.com/watch?v=tQP4IsnIAXo
Followed closely by 179 in 2012. Clever, just clever. Hanging under the bridge instead of on top of it. A brilliant creation. Watch the end of this video to see the bridge shenanigans.
https://www.youtube.com/watch?v=lplARY6PPUQ