Retro Game Crunch is a $1 collection of small but different indie games.
Soma Spirits is a $0.50 JRPG and actually fun.
Hexcells series is a nice bunch of nonogram-like games, Infinite also having a metric fuckton of extra puzzles tucked away on the side too.
Sinless is really short but presents a supremely fucked up cyberpunk dystopia initially seen from the perspective of the near-top civilian population for $0.50.
Hero of the Kingdom 1 and 2 (and 3 but that's not at a good sale price yet) are a strange mix of resource management, hidden object (sort of but not the actual genre), and p&c adventure.
Pony Island is fucking weird for an 'arcade' game. Runner, exploration, puzzle...
Actually most of the stuff on sale is under $1. Double under between $1 and $5.
I could keep going but you get the idea. There's good stuff that's very cheap so you don't wind up wasting too much if you choose to buy. But you really gotta dig. A lot of things are also very very short like Refunct which is a parkour game while for me most puzzle games are painfully brief.