Dry Bones would be a great enemy that's gotten some recent popularity in Mario Party
Wigglers could be rarer, but more powerful enemies
A simple enemy that causes flame damage
Obviously, we need Thwomps to...well...thwomp some things
Dragons from Super Mario World would be a great addition
How about some bloopers? If there's any stage with large amounts of water, these guys are a necessity
I wonder what these things could do. I think I saw them in a Mario game once
A perfect choice for dark stages, easy enough concept too
Chuck Chargers are so annoying, but they still deserve an appearance
Do I need to say anything for him?
Dinorhinos. Just the name itself is awesome
Cobrats from Super Mario Bros. 2 would be an interesting addition I think
Flurries would just be flat out fun to smash to pieces
If these things didn't annoy the crap out of you, I don't know what will
Pokeys from Super Mario World and Super Mario Bros. 2 + 3 were sometimes difficult in later stages make them difficult to defeat in Smash Bros. too please!
Make Lakitu appear as a mini-boss!
With thousands of various enemies from the Mario Bros. series, it shouldn't be too hard for Sakurai to come up with a couple of real enemies, rather than those stupid things with beam swords who looked like mentally insane duck-human hybrids.