Half Life: 2

Alyx - models/player/alyx.mdl
Barney - models/player/barney.mdl
Breen - models/player/breen.mdl
Burnt Corpse - models/player/charple01.mdl
Zombie - models/player/classic.mdl
Combine Soldier - models/player/combine_soldier.mdl
Prison Guard - models/player/combine_soldier_prisonguard.mdl
Combine Super - models/player/combine_super_soldier.mdl
Corpse - models/player/corpse1.mdl
Eli - models/player/eli.mdl
Gman - models/player/gman_high.mdl
Kleiner - models/player/Kleiner.mdl
Magnusson - models/player/magnusson.mdl
Father Grigori - models/player/monk.mdl
Mossman - models/player/mossman.mdl
Odessa - models/player/odessa.mdl
Stripped Soldier - models/player/soldier_stripped.mdl
Zombie Soldier - models/player/zombie_soldier.mdl
Fast Zombie - models/player/zombiefast.mdl

Day of Defeat

DoD American - models/player/dod_american.mdl
DoD German - models/player/dod_german.mdl

Counter Strike

Artic - models/player/artic.mdl
Gas Mask - models/player/gasmask.mdl
Guerilla - models/player/guerilla.mdl
Leet - models/player/leet.mdl
Phoenix - models/player/Phoenix.mdl
Police - models/player/police.mdl
Riot - models/player/riot.mdl
S.W.A.T. - models/player/swat.mdl
Urban - models/player/urban.mdl

Civilan Models

Male 1 - models/player/group01/male_01.mdl
Male 2 - models/player/group01/Male_02.mdl
Male 3 - models/player/group01/male_03.mdl
Male 4 - models/player/group01/Male_04.mdl
Male 5 - models/player/group01/Male_05.mdl
Male 6 - models/player/group01/Male_06.mdl
Male 7 - models/player/group01/Male_07.mdl
Male 8 - models/player/group01/Male_08.mdl
Male 9 - models/player/group01/Male_09.mdl

Credits to rob54362 for the player model list!