Pesci really was outstanding in "Goodfellas". He captured that "loose cannon" quality, and (in my opinion) upstaged DeNiro in the scenes in which they appeared together.

The scene in which Pesci shoots (and kills) Spider (the kid who was slow in serving drinks) blew me away.

BTW - That kid (Spider) was portrayed by the same actor who plays "Christopher" on "The Sopranos" (Michael Imperioli).