$4 on Steam, any votes on what I should get?

TBC or Shank 2.

Sine More is only 3.39 as well and its awesome.

super hexagon?

Sine Mora is a damn fine SHUMP, and it's only $3.39 right now. AudioSurf is also hella fun. :)
And Trine 2 is a great choice. If I had the money to get it now I'd do so, especially since I have a coupon that stacks with this sale.

You can also check Here for stuff on steam that are on sale for $4 or less, like OMD2 or Hell Yeah or Alan wake American nightmare, which I heard are pretty good games :D

The Basement Collection (I don't have, but it looks really good :D).

Wait for Winter Sale IMO, otherwise what you have here is pretty good. Basement collection is a decent pick as well.

Also, if you don't have it; you can likely trade $1-2 Steam Wallet for a Humble THQ Bundle on SteamTrades.

Also, Limbo and Audiosurf are only $2.50 each :)

Trine 2 is my choice for you.

sine more or TBP

Shank 2.

Trine 2 is fantastic, but better in coop than solo. I'd also recommend Geometry Wars if you end up with an extra dollar to spare. Pretty basic twin-stick shooter, but it's a lot of fun.

the basement collection

Trine 2 is an amazing game! Go get it.

Trine 2 ftw!

I'd definitely choose Trine 2. That's an awesome game :D

TINY AND BIG

they bleed pixels is awesome <3