Currently looking at the first two characters, COP and NINJA. Here are the current ideas of how they will act in game.
The cop has an arsenal of guns and other gun-shaped equipment, which allow him to fire different types of rounds (standard, exploding, ricocheting, freezing, magnetic) in different patterns (standard, rapid, burst), as well as activating defensive fields of different sorts. His battery pack automatically regenerates in the light (solar power!) and isn't able to work underwater or in extremely hot locations... unless he finds a better one. When playing with friends, the Cop is a MUST - ranged attacks support any other character, and his exploring abilities, for the most part, can be used by the entire group (for instance, when he blows apart a wall with the explosive rounds, everyone can walk through).
The Ninja also has a great variety of tools to help him defeat his enemies and explore, but of a different nature. He uses throwing stars for a slightly weaker ranged attack, but has the ability to strike close enemies with a deadly bear claw. The ninja knows how to construct a deadly bomb, and to lure nearby enemies into its range, without putting himself in dangers way. Additionally, the ninja can cling to some walls (and maybe climb some others) with his bear claw, and dash out of harms way, or though his enemies for a running attack. It is said that the ninja can go so fast when dashing full speed that he can manage to even go through some solid objects... When takling an objective on your own, the ninja is a good choice - high mobility gives you a good chance at survival, but many of the ninja's exploring skills don't allow your group to follow you.
Naturally, don't expect to see everything here in the game, but you might see some of it!