Saint's Row IV and Civilization: Beyond Earth are both free to play on Steam this weekend. Both are good to go until Sunday, 1PM PST. Try 'em. If you like 'em, both are on sale over the weekend, too. $5 for Saint's Row IV (just ahead of the standalone Gat out of Hell expansion), $30 for Beyond Earth.
Both are good weekend games. Saint's Row because you can just romp around in the sandbox for a bit, Beyond Earth because it won't be able to suck hundreds of hours from you (unless you end up buying it).