This one came out of nowhere.. iOS version out soon which will be cross play capable with Android users.http://cs-portable.com/
It's free on the Android market right now.
Played it for about an hour yesterday and I'm going to say it's the best Android game I've played to date. I spent most of my time playing the Zombie mode on a 12 player server (there were a few 32 player servers as well) turned out to be a hell of a lot of fun. It starts out with one person being chosen as the "zombie" and then having to infect the other players. Once a player becomes infected, they join the zombie team until either all the humans are infected or the zombies are killed off.
Never noticed any lag playing over Sprint 4G (WiMax). The website claims it's playable over 2G as well.
Tried a quick round of basic team deathmatch offline with bots, which definitely had a classic counter-strike feel to it. The bot AI was a little too good though, was finding myself killed with barely being able to get a single round fired. No option to change the bot difficulty.
You can play in first or third person.
Over all very impressed.. especially considering it's a free game.