Hey, the games I like to play the most are the first person shooter ones, online. I like to compete againts other players over the internet. The best game I've ever played is Empires, which is a HL2 modification.
The game consists on two factions that are on war, ones fighting for freedom and the others for the world domination.
It mixes the first person shooting with real-time strategy. There is a commander that leads their team, drops structures over the map like turrets or refineries, creates vehicles, gives enemy targets... etc. And the rest of the team fights on foot or using vehicles. It's a good game. If you own a copy of Half-Life 2 download this modification, it's free.