Whats the best 5$ you can spend on steam?

Anything thats worth playing.

I got FTL (Faster Than Light) for $4.99 on sale a few weeks ago. I recommend it :)

super hexagon is pretty fun... in a smash your computer kind of way

it's in the current humble bundle, but i think its $3 or so on its own on steam

Also recommending FTL: Faster Than Light, but it's only $5 when on sale

Lone Survivor looks like another really good game from everything I've seen if you like survival horror

And I managed to get Borderland 1 for $5 during the Winter sale.  Great purchase that was

Any of the classic Tomb Raider games for nostalgia.

humble bundle, $5 USD get 4 games, most that are quite fun. Choose how much you want to donate to charity and etc.