Turtlefox
Smash Cadet
i feel like it will bring an amazing new style to brawl and would love to see many assist trophies.
It wouldn't really be all that new... in terms of gameplay. It's essentially pokeballs for other characters outside of the pokemon franchise. Nevertheless, it's still a nice feature.
Anyway, I'd love to see some more retro assist trophies in their 8-bit glory like the already confirmed excitebike.
More specifically: Bub and Bob from Bubble Bobble! It'd be awesome if they like chase after you and trap you in a bubble. Or at least like blow some thunder bubbles to give you a little stun. Or a bunch of loveable red eyed white hooded Stoners.