Prince of persia

Critter Crunch

that or save it for a rainy day

have lots of music and an action packed tetris game?

audiosurf

want a flying racer?

skydrift

Save it.

PuzzleQuest: Challenge of the Warlords

Buy secret of the magic crystals. It's only $1,99.

Penny Arcade 3 or Dungeons of Dredmor

want horror and adventure?

post mortem

want a visual novel type?

analougue: a hate story

The best you cna get on your money

Foreign Legion Bundle

S.T.A.L.K.E.R.: Call of Pripyat

i have 3.80 ?

Sacred Gold is 1.99$ at the moment.
The Witcher Enhanced Edition Directors Cut is 2.49$.
Audiosurf is fun (2.49$).
And Binding of Isaac is 2.49$ at the moment, but you probably should get it with the DLC, as it adds a lot of content.
And then there is S.T.A.L.K.E.R. Clear Sky for 2.49$.

!!!!!!BAD RATS!!!!!!

Sonic CD

the answer is always fortix

Assassin's Creed 1 director's cut... you won't regret!

Audiosurf or get The binding of Isaac + DLC from the actual Humble bundle 7 for $1

two copies of fortix and one copy of bad rats.

Analogue: A Hate Story

Botanicula, World of Goo, Syberia or Waveform+Zen Bound 2.

put it in your monney cannon and try to aim at gabe and shoot pennies to him!

the witcher

buy limbo dude

Get a TF2 key.

A Bard's Tale. I would if I could. It is countless hours of fun.