Modern Combat Domination is a first-person shooter for the Mac. It currently ranks #38 in the top 50 paid apps on the Mac App Store, which is no small feat. The game features nice graphics, both a single-player mode and a multi-player mode and a nice ranking system. Honestly, you will only enjoy this game if you don't start comparing it with beast games like Call of Duty and Battlefield. This is a small-budget game, with its flaws, but fun nonetheless.
Modern Combat Domination doesn't have a single player campaign, but it does let you play against computer player in any of the available game modes. The multi-player mode lets you play against real people over the Internet or a LAN.
The graphics are nicely optimized for the Mac. I thought the game was surprisingly smooth, considering how bad Macs are at gaming. I had some problems with the mouse sensitivity, but I am pretty sure that is because my mouse is not the best one.
I tested the Multi-player mode, and when I logged in, only 170 players were online. That basically means that you might have problems finding a good match. I managed to play against a single opponent for 5 rounds. The game was about defending two points in the map. Suffice it to say, a 1 on 1 game in a large map can be boring.
All in all, Modern Combat Domination is a nice game. It doesn't have the best physics engine or top-notch graphics, but it can be rewarding in other ways.