I'd say Rush is a must-buy at $1.69 if you are into puzzlers. Haven't put much time into it yet but seems quite polished. It's developed by the same team behind Toki Tori, which was excellent.
Pretty awesome deals today. Amnesia is only $6.80 ($4.80 if you have Penumbra from the Humble Indie Bundle). Must buy for any horror fan.
I also picked up The Ball, Dead Space, and Swords and Soldiers HD.