Ice Rink Half-Pipe
Build a 10-12 foot high half-pipe in the middle of the ice rink. Everything is normal about the ramp with the exception that the flat area is not wood, it's ice. So, essentially it is two quarter-pipes facing each other to make one full half-pipe. Get a bunch of skaters and BMXers to try it out. It's a little like the gauntlet . . . perhaps have hockey players fire pucks at them while they are skating.