Free MMOFPS or Free MMORTS

Savage 2

Savage 2 is a MMO that features action FPS combat for some players and RTS command controls for the commander players of each team.

Soldier Front

Soldier Front has real military personnel and weapons in a highly realistic FPS.

Sudden Attack

Sudden Attack is a high paced violent MMOFPS that has 5 different game modes and features underwater action.

Tabula Rasa

Tabula Rasa was a pay-to-play game from NCsoft that ended on Feb 28, 2009. In its final days, TR was free-to-play.

Tremulous

Tremulous is a free, open source game that blends a team based FPS with elements of an RTS.

WarRock

WarRock is one of the oldest free online shooters. Players can fight in the air, sea, or land with a wide variety of vehicles.

WolfTeam

WolfTeam is a free MMOFPS/online shooter where players can transform into werewolves. WT also has an interesting weapon system.

Valkyrie Sky

Valkyrie Sky is a vertical scroll shooting game aka MMOShMUP (MMO Shootem Up). Scroll shooters were big in the 1980s.