I have a 2010 11.6" MacBook Air, so I know that there's a lot of gaming options open for you on your machine:
Shadowrun Returns/Shadowrun Returns: Dragonfall Directors Cut - SRR is fantastic for its use of a very unique fantasy/sci-fi setting; a kind of mashup of Tolkein-esque fantasy with a William Gibson-esque cyberpunk dystopian future. SRR was critcized for its linear campaign and initial UI/gameplay limitations, but I enjoyed it on the strength of its writing and main campaign. The Dragonfall DC (a standalone expansion) has been lauded as being pretty much more of SRR but with none of the original game's flaws. The developers are doing a new Kickstarter for a third game, set in Hong Kong.
FTL: Advanced Edition - A highly-lauded rogue-like starship combat/management simulator that lets you indulge in all of your fantasies of commanding ships in the Star Trek/Star Wars/Firefly/etc. universes, that landed on many people's GOTY lists in 2012. In 2014, the game got a free massive content update in the Advanced Edition.
Avernum 2: Crystal Souls - the latest installment in Jeff Vogel's (in)famous series, known just as much for its deep, immersive, huge game world, as it is for its rather sparse graphics and sound. Still, it offers a massive amount of gameplay for the price. And if that isn't enough, you can play Avernum: Escape from the Pit, as well as the games in Spiderweb Software's Avadon, Geneforge, and original Avernum series.
NEO Scavenger - a hybrid RPG/desperation survival game that's one-part Fallout, one-part Choose-Your-Own-Adventure, and one-part DayZ, with a very deep crafting and survival system. Capping that all off is a surprisingly brutal combat system that lets you get down and dirty with your opponents (You tripped the bandit that was trying to rob you with a leg sweep...do you try to crawl away to safety, or do you try to use your glass shiv to finish him off?)
Drox Operative/DO: Invasion of the Ancients - A very addictive, very grindy space-based action combat RPG where you're given a ship, cast off into the galaxy and told to pretty much do whatever you want. Make alliances, do quests for other races, gain their favour, and then crush everyone else in the galaxy, or troll races with propaganda and sabotage, for fun and profit. Watch out for the Ancient factions though: they're a little harder to take down than the others...(Especially those f$@&%*# Veteran Destroyers.)
