Any good open world coop games?

I want to play something with my friend. We have played alot of coop games and we got bored of them. Do you know any coop games that wouldnt be neccesarily open world, but we could go from mission to mission and such, maybe stealth or something.
Some of the games weve played:
Saints row 3,4
Gta 4,5
Borderlands 1,2
Payday 1,2
Guns of Icarus
Minecraft
L4d2
Magicka
And so on. I'm telling you what we played so nobody would suggest the games we already played for hundreads of hours.

Modern Warfare 2

Modern Warfare 3

Splinter Cell: Blacklist

Destiny is coming out this September 9th which sounds like it's going to be a great open world co-op which is apparently designed to feel like a single player, interesting concept and looks great.

There's more info and an anticipated review here: http://www.tradeindetectives.com/blog/destiny-overview-trailer-and-review/

But as for currently released games how about
Halo
Dead Rising
Splinter Cell

"Any good open world coop games?"

Sacred 2 is a top-view, open world, action RPG. Aside from the normal story-mode the game also has a 'Free World' option that removes the story-line quests and thus removes any story-related inhibitions like having to have finished a certain quest to gain access to a new area and enables you to explore the world at your own pace and leisure. The game can be played with up to 4 players simultaneously on all modes and difficulties.

Dungeon Siege 1, 2 and 3 are action RPGs that can all be played cooperatively with up to 4 players simultaneously. One thing to note would be that the DS2 official GameSpy server has been shut down as of last year after 8 years of service so you'll have to either play on LAN or create a server of your own. I'm not sure if it works with Hamachi. Also keep in mind that Dungeon Siege 3 works and plays fairly different from the first two (produced by Obsidian instead of Gas Powered Games).