I really liked this idea:
Throwing Weapons - So many options for customization here. Players could pick their weapon, just like we already do for other sets, amongst options like knives, skulls/bones, shoes, javelins, etc. Make it a Ranged Blast S/L set with a concentration on fast, lighter-damage attacks. I know, it sounds like Archery, but with more customization options! It'd be the equivalent Scrapper Claws choice, but for Blasters and Corruptors... and maybe Defenders.
As for my own:
1. Animal Spirit Control (Controllers/Dominators) - I was thinking that an Animal set for MMs might be good, but it doesn't really sound too Mastermind-like to be the evil ruler of a band of critters. Although I do like the idea of a squirrel version of Gang War. Anyway, I reworked it into a possible Controller powerset. Most of the controls would work like temporary pet summons. You want to hold someone, you activate the power "Bear Hug" and it holds the enemy with a ghostly-green image of a bear embracing them. You want to disorient someone, so you summon the spirits of birds to constantly wizz about their head. Stuff like that.
2. Elementals (Mastermind) - Basic premise being that you summon elementals as your pets. We already have some current in-game options for this. Look at the Magmite Lords in the Hollows. Or at simple ole Fire Imps.
-Minions: Fire Imp models with Fire Blast powers
-LTs: Magmite Lord or Devouring Earth Sentry models with Stone Melee powers.
-Boss: Elemental Storms from the Shadow Shard "models" to provide energy damage and some control.
A little bit of damage from fire, smash, and energy. It'd go great with /Storm too!