Vector is an Android OS game that centers around free-running. It's got a simple story of your character trying to escape an evil corporation, and you run along building tops to escape an agent sent to neutralize you. The game is pretty fun, especially if you're a fan of parkour. It's got simple controls with a few extra features and unique things thrown in. I recommend the game, but it's almost 50 MB, so watch out if you're using a limited data plan on your device. There's a free version with 20 stages and a deluxe paid version with 40 stages.
I downloaded this game back when it was just starting up and didn't even have all of its stages. That was more than a year ago, and I still play it to this day. It's just a very easy game to pick up when you're bored and have to wait for something. I still haven't beaten it yet, it gets very hard to get every star as you advance, but it is still lots of fun, so I can't complain.
I still haven't beaten it yet myself, as far as three-starring every level goes. I completed every mission, but some of those were one stars, and I can't stop until I've gotten every last star. It's just an addicting game that's always a challenge and always fun for short bursts. I try not to get sucked into it to the point that I'm playing for like an hour each time, though.