From Worms Knowledge Base
This object is placed on the terrain like a mine. It explodes when hit, but until then it's only use is in amplifying the jump of any worm that lands on it. The more the worm jumps in it, the more powerful is the jump. It can be used by any worm.
This should be simple to program, as it basically a less-powerful barrel with a different animation. Amplifying the jumps of worms that land on it may be more tricky, but it would be similar to applying low gravity to the worm during his jump.
If a worm is in the way, i.e. sitting on the trampoline while another worm is trying to use it, the trampoline will not react to any jumps. This utility could offer the occasional advantage when a particular cliff is just out of reach, or a particular crevice too far across. Also, it could be used to gain a higher backflip from which to activate the parachute and float across the terrain. It would also allow a cushion to fall onto if you plan to drop from a high perch.
The trampoline might be limited in it's uses but it would make a great tool for fun manouvres, possibly in conjunction with the rope.
Trampolines could also perhaps be made available on the terrain in certain positions when the game begins, given a suitable editor. This would add extra variety to the "Battle Race" scheme.