I guess many characters should have more melee attacks AND the normal one too.
Freezer - Tail attack
Cell - Tail attack (with leeching)
Vegeta - Charged bihanded smash (like when he finished Goku in Buu-Saga)
Piccolo - (don't know the english name, but you know, the one where his arms get longer and longer); I guess it would not be too difficult to code, would it?
and so on