Although not near as popular as the MMORPG genre, MMOFPS games are gaining steam since gamers want more action in their MMOs. While most MMORPG combat systems require little to no hand-eye coordination, the MMOFPS focuses on intense combat in a persistent world. 

MMOFPS: The Next Big Thing in MMOs?
GameOgre.com takes a look at the emerging MMOFPS genre. 

GunBound  
Free massive online shooting game.

Control Monger
Free online FPS where bots go to war! 

Endless Ages - Review
One of the first MMORPGs with a first person shooter theme.

Face of Mankind 
MMORPG set in the 24th century where players are allowed to make the missions. 

Gunz The Duel  
Live out your fantasy of being an action hero.

Huxley  
Easily the most eagerly awaited MMOFPS. Could define the genre even better than PlanetSide. 

Neocron 
Easily one of the most controversial MMOs with such features as a seedy red light district, foul language from NPCs, and extreme violence.

Neocron 2 
Sequel to one of the first truly controversial MMOs. 

PlanetSide - Review
First person shooter MMORPG that features vehicles, squads, and hacking.

World War II Online 
MMORPG that combines several gaming elements (RPG, action and strategy) into one massive battlefield.