Good coop games

I’ve been playing a lot of coop games with my friends this summer and I thought I’d ask you guys for some advice.

Some good coop games I’ve found:
Ratchet Deadlocked-Funny storyline and a ton of creative guns, enemies and explosives makes a very hectic and awesome game.
Dynasty Warriors 3-Strangely addictive button mashing fun.
Any Tales of Game-Great four player rpg.
Twisted Metal Black-Versus mode is fun, but coop mode is a little too difficult. I just got the game though so I might like it more once I play more.

Right now I’m looking for a good coop rpg, hack and slash game or anything like the games I mentioned above. Advice on any coop game would be appreciated though.

I played through Halo 3 and Gears of War 2 and Tales of Vesperia with my gf. We had tons of fun doing it.

An oldie but goodie would be Secret of Mana. If you have a Wii you can download it off of the VC.

Tales of Symphonia was pretty fun four player.
And by fun, I mean obscenely easy since you can just stunlock a boss with all four players beating on it so fast.

SPLOSION MAN! The co-op mechanic in this game is fucking genious. The idea of "dual ‘splosions’ gets annoying after awhile, but I haven’t played a game that emphasized working together to get through obstacles in the way this game does in years, if at all.

If you or the person(s) that you’ll be playing with has an XBox 360 you might want to look into Castle Crashers. You can purchase it off the marketplace. It’s a pretty sweet game. It can be one player, but it’s way more fun as a coop with up to 4 players. It from the NewGrounds guys so it has an intersting visual style and storyline. At it’s base I guess I would call it a 3D side-scrolling action RPG.

Edit: Also, Army of Two is pretty good. It’s similiar to Gears 2, only has a huge emphasis on teamwork through the Agro System (whoever is doing the most damage to the enemy will draw more fire, allowing the other player more safety to advance). The downside is that it’s a short game.

Hmm…I could think of quite a few.

Trauma Center: New Blood - Good Coop, but you’re bound to get frustrated on something.
Streets of Rage Series (or most Beat 'em ups in general)
Metal Slug Series
Boom Blox - Very fun and interesting co-op there.

Damn, Soma Bringer would be excellent for what you described, but so much for getting your hands on that. Also makes me wish Phantasy Star Zero would come out sooner instead of having to wait another 2-3 months. PSZ has damn good multiplayer with pretty much no lag on Wi-Fi from what I played with the JP version.

Wolf Of the Battlefield 3 in the PS3 store is a fun game for not only two, but three players at the same time. Almost like gauntlet with GUNS. (Which reminds me: Get Medieval. Hilarious and competitive dungeon scouring.)

Get MAME on your PC, connect it to a tv and play to your heart’s content. Esp. games like Punisher or Knights of the Round.