Heres a unique idea:

Flipper Arena

The Flipper Arena has 4 starting squares: 1 in the middle of each wall. The arena is 20m x 20m. The walls are 25m high, so it is impossible to flip another out of the arena.

This is where the hazards come in. The floor is covered with 9 floor flippers: one in the center of the arena, one in front of each starting square, and 1 in each corner. If you try and flee to the starting squares to prevent getting flipped from the flippers, youll be crushed by a huge 300kg hammer hidden behind each starting square.

Your bot will never be safe in this arena!

Mwahahahaha!!!!