Here are some of my ideas for ground units: AOE units to counter swarms of smaller units(think of SC2 Archons/Colossi). True swarm units with almost unparalleled stats, that fall to AOE units unless split up very well(think of SC2 marines). Skirmisher units with decent speed, long range and low HP that would be able to kite conventional units, but would fall to units that can get on top of them quickly and then easily beat them in a straight up fight. Anti-massive units with very high alpha, but with low attack speed and projectile speed(making dodging their shots for faster units a piece of cake). Raider units with excellent speed and very high DPS, bad survivabilty. Special ground raiders with cliff-jump abilities. Crawling bombs and gap-closing/jumping bombs. Units which can transform between air and ground modes. "Converter" units which can make your opponent's units switch sides. Disabler units with slowing/paralyzing/immobilizing attacks. So that's just brainstorming and recycling ideas from other games. Also, what kind of cool unit ideas have you guys got?
I've posted a lot of my unit ideas here: https://forums.uberent.com/threads/new-unit-suggestions.50715/
Yeah. There's already a thread for this. you should post there. And perform a search next time before posting.