I personally think the top spot should go to the Spindrift from Super Mario 64. Jumping on one of these boosts your air time, lets you glide soothingly down afterwards, and probably even smells nice, considering you're near the flower on its head at the moment of the stomp.

Real number 1: Jumping on top of a Toad inside a Mushroom House in NSMB Wii

Spiny should be number one since jumping on it relieves you from the pain of existence

Think it would be pretty painful