Any suggestions for Co-op games on the winter sale?

L4D2 and Borderlands 2 or 1 (both GoTY)

2d platformer: Trine 1&2, up to 3 players

SHMUP: Jamestown, up tp 4 players

Hack'n'slash: Torchlight II

Sandbox: Just Cause 2 multiplayer, Terraria

Valve games: CS:GO and L4D2

That's all I have on my mind. Maybe others will name better games.

UPD: And yes, Borderlands :) (thank you, JB567)

Payday 2

L4d2,Orcs Must Die 2,Dungeon Defenders,Nation Red,Payday 1 & 2.

Payday 2, Borderlands 2 GOTY

Killing Floor, Hammerwatch, "Garry's Mod", Lunar Flight(don't know if its good, look intresting so), Magicka, Serious Sam(yeaahh, yeaaaaaaaaaaaaaaaaaaaaaaaaaaahhh), Warframe, Moonbase Alpha(well, it's fun huehuehue), The Ship(not coop, but amazing)LotR:WotN(3 coop, not 4, sorry).Risk of Rain.

ps. Local coop: Adventure Time! Explore the dungeon.... and Legend of Dungeon :3

and there's is this https://www.humblebundle.com/yogscast too

Starbound, Payday 2, L4D2, Garry's mod, Torchlight 2, etc...
If you want a Local (offline) co-op, you should go with Brothers: A Tale of Two Sons, it's amazing!