What is the best game on steam for under 10$ at the moment?

I'd personally recommend Buy Cthulhu Saves the World & Breath of Death VII Double Pack for $0.44 (it comes with steam cards so it's even cheaper):

http://store.steampowered.com/sub/8848/?snr=1_7_7_204_150_2

Here is a list of games that are sorted by user reviews:

http://store.steampowered.com/search/?snr=1_4_4__12&term=#sort_by=Reviews_DESC&page=1

Here is a list of games sorted by user reviews and are on sale:

http://store.steampowered.com/search/?specials=1&os=win#sort_by=Reviews_DESC&specials=1&page=1