In SMB: Hammer Bros.
Mario games in general: I'm surprised nobody mentioned the Muncher yet. Quoting Kernigh:
Originally posted by Kernigh
Munchers, rooted to the ground, always munch, never rest, always chew the air until something else comes there. A terrible magic grants to each muncher a hunger never satiated and an endurance never outlasted. Munchers will bite without pause until the end of time.
. I could post stuff now and then
My Assembly for the SNES
tutorial (it's actually finished now!)