Last Level and SOFF Games have developed a vehicle based MMO shoot em up: Steamcraft.
Business Model: Retail Purchase
Build Your Own Battlecraft: Whether for ground or air combat, you can choose from over 600 building components and 40 weapons to design the weaponized vehicle of your dreams, and your opponent's nightmares.
Physics: This game has em. Watch pieces of your opponent's vehicle fall off as you punish them.
Multiple Modes: Play in Deathmatch, Team Deathmatch, or Capture the Flag modes.
Cha-Ching$!$!: Sell your vehicle designs on the in game market to earn in game currency.