Notes:

Kirby's U-tilt in Smash 64, seen in the debug menu.

Yellow cubes are his hurtboxes, Red ones are the actual hitboxes.

Due to the speed of the move and huge disjoint, it can be used to clank with projectiles, as a combo starter, anti-air, low-% juggler and shield breaker. It's regarded as one of the best moves in the entire series.