I have 15 bucks. Which Game/Games should I get?

Starbound, you have a endesly list of planets , you can explore and play multiplayer with friends , very cool game

You should get bundles instead, at bundle stars they have pretty good bundles such as the brutal bundle

Risk of Rain is pretty cool and its only $10, with the other $5 you could get The Binding Of Isaac

humble x bundle + humble weekly and for the rest of money as many as you can buy fortix copies!

Bad rats...?

Some LEGO games of your favorite franchise on GMG? Remember to use discount codes!

GMG25-0YUM5-VKMVU - 25% off almost anything

1WDO6K-KWDFJQ-U1E7AI - 25% off almost anything as well I believe.

I got both LEGO Harry Potter games on GMG for steam the other day for 7,50€ which is a quite good deal in my opinion.

7 copies of Braid!

blockland?

Braid, now

The Secret World is 66% off. Cheapest I've ever seen it.
Myself, I'm still on the fence about it. I'd like to buy it but I don't think I'll play it.
Either way, the offer ends in 30 minutes.

State of Decay, an actually really good open-world zombie survival game that you can easily get for a buck or 10 through trading at the moment. Playing it myself and even if it has it shortcomings it does so much right (not focused on killing but on exploration, perma-death, etc.) that I completely forgive the weird clipping and stuff like that

Don't Starve

state of decay , tomb Rider

Spec Ops: The Line is currently on sale in Steam. Buy it.

Fallout new Vegas or Fallout 3

if anything then why not Battle vs Chess

Thats depends, what kind do you like? Portal series, SimCity Deluxe, World Of Goo, Left 4 Dead series, GTA San Andreas, Worms, Assassins Creed series. Those are very cool games that I recommend.

Wait for the Martin Luther King Day sale.

CSGO

Depends. You want newer games? Older ones? AAA or indie? Any particular genres? You have to be more specific. And like someone already said: right now, Spec Ops The Line is on sale. It's pure genius in terms of story and narrative. It's not the second coming of Jesus in terms of gameplay, but it's worth it for the story alone. It's that good. Worth every penny of a measly 5 euro.

Rust, you can get it for 6-7 TF2 keys which is about $12-14.
Also Prison Architect and Project Zomboid is in that range.

Rust

Rust

Don't Starve it's a great game! :)

Deus Ex HR was pretty good. Not sure how good the Director's Cut is though. I'm sure you can still trade for the original if that's meant to be better.