Party games on Steam with local coop

I've had a lot of fun with Hammerwatch and a few friends, maybe try that?

Timm, try this http://store.steampowered.com/app/285900

edit: if you dont want to spend money, i can check your game list

edit 2: you have this, looks fun in a party with friends http://store.steampowered.com/app/301970/

Borderlands 1 or L4D with split screen mod.
EDIT
"can be played simultaneously with a drinking game"
Some Worms game? Like Armageddon ;d

mercenary kings?

maybe this http://store.steampowered.com/app/116100/

This game is super fun http://store.steampowered.com/app/251470/

I love local coops, well, just a few:
Injustice, Mortal kombat
How to survive
Fight the dragon
Castle crashers
Trine 2
Speedrunners

Does it have to be coop? If not then I suggest Speedrunners.

EDIT: Rayman Origins is pretty sweet when it comes to coop action.

I can`t think of a good drinking game, but at least you know what beverage fits with this game : http://store.steampowered.com/app/275390/

(4 player co-op with controller support)

This one looks fun and could be played with a drinking game http://store.steampowered.com/app/269030 (at least looks fun to me) :)
And from your list of games perhaps this one http://store.steampowered.com/app/212480/ ?

The LEGO games are not only really fun, but can be played when both players are intoxicated

Speed runners, castle creashers, or battelblock theatre are all pretty good. Im not to sure how good they are but that is what screencheat and/or starwhal were made for.You can check out the Jackbox Party Pack too. Some of those games are pretty fun if you want more average party games as opposed to "video games" (shooters/racing/ect)

Nidhogg, screancheat, thief town

This are the games I have that have local coop:

http://i.imgur.com/Ud45Bo3.png
http://i.imgur.com/ikhSFwZ.png

BattleBlock Theater and Castle Crashers are good local coop games.

Divekick has no coop but good for drinking party:

Serious sam 3 BFE [up to 16 players co-op] but i think 4 players local minimum

The Expendabros

Haven't played it myself but it's free and might be entertaining.

magicka?

Some racing games, especially wacky ones, and so much this one: http://store.steampowered.com/app/212480/
I guess some arcades of Sonic's universe might have local co-op too.
And yeah, Castle Crashers sounds like a lot of fun for a party too and can be played while drinking, I guess.

BattleBlock Theater all the way

Hmm, here's a few that my girls and I play on the weekends

Rocket League
MKX
Broforcee
Magicka
Unreal Tournament 3 [takes a little rocket science to get local coop working]
Renegade OPS
Sonic Racing Transformed
Lara Croft Guardian of Light & Temple of Osiris

Also here's a couple i have but have yet to try buts know supports local coop

B.U.T.T.O.N. (Brutally Unfair Tactics Totally OK Now)
Speedrunners
slam bolt scrappers
Left 4 Dead 2

do you like mario kart? sonic all stars racing transformed is a great kart racing like mario. You can even play the "singleplayer" in co-op/multiplayer

What about brawlhalla? You can play in local coop or pvp

Check this one out its on my wishlist but since its online is lan only it not makes sense for me:)Hope you have fun!

This website always help me ->
http://pcgamingwiki.com/wiki/The_Big_List_of_Local_Multiplayer_Games