Call of Duty Offline.
Call of Duty 4 Modern Warfare has a decent short campaign. The story is quite interesting, and there were few moments that made me say "Woah." The concept of Modern Warfare is exactly the same as the other Call of Duties. You receive a mission, you follow it, and you kill enemies in the process. There are some parts wherein you'll be using the AC31 Aircraft or riding on top of a truck with a machine gun. The campaign is simply fun to play.
For veteran mode, the first few missions were mild and fun. When you get to the middle part, it get's much more difficult and intense. There are parts that I got stock to for about a week, and there are parts that I just stopped playing. Veteran mode is quite challenging and tiring, but you will get it after you die for a few times. What annoys me most about the campaign on veteran is that the enemies has infinite respawn. You can just man a machine gun and kill enemies for the whole afternoon. And what's more to it, your AI allies are just dumb. They will never move unless you lead them. You can't just sit on a corner and wait for them to clear the room. Overall, it's challenging though still fun to play.
The graphics of Modern Warfare is good enough for a 2007 game. The guns are detailed, the terrains are vivid, and you can just feel the vibe of capturing Al Asad. The blood is pretty well done. It's bloody, but it's not that violent. When you snipe an enemy at the head near a wall, the enemy's brains will splatter on the wall. Though don't worry, the blood is a bit pixelated and it's not that gruesome. The graphics are neatly done.
What I like most about this game are the achievements. The achievements are simple and easy. I like collecting achievement gamer scores on the 360 and showing it off to my friends. Because of Modern Warfare, it gave me 1,000 gamer scores.
If you like the Call of Duty Series and you like the taste of some classic FPS, buy this game and you will have some decent fun with it. Good luck on getting all the achievements if you're an achievement hunter.