Steam is one of the go-to places for PC gaming, as they have nearly every single PC title available (with exception to EA games's, as they now have their own platform to compete with Steam's)
Bastion, $4.99 USD, Soundtrack Edition for $8.23 USD
This is apparently one of the best-valued games according to a friend, and it makes you cry at the end. (<3 Sona)
Anyways, if you want some good deals on games, check out www.steamgamesales.com. They have games from tons of different services, all with the ability to activate on Steam.