Main games: L4D, CS:S, TF2, ZM, HL2.
Source mod: zombie panic, synergy bla.la...

Download the best single player mods on the bottom of the text.
other and multiplayer mods here (bellow)
hl2 is needed.




----------------------------
SINGEL PLAYER:
-----------------------------
1.http://www.moddb.com/mods/research-and-development
2.http://www.moddb.com/mods/modular-combat
3.http://www.moddb.com/mods/r-e-b-e-l-l-i-o-n
4.http://www.moddb.com/mods/dear-esther
5.http://www.moddb.com/mods/the-event-in-village
6.http://www.moddb.com/mods/joutomaa
7.http://www.moddb.com/mods/project-25
8.http://www.moddb.com/mods/the-citizen
9.http://www.moddb.com/mods/penetration

------------------------
MULTIPLAYER
------------------------

1.http://www.moddb.com/mods/zombiemod-source
2.http://www.moddb.com/mods/neotokyo
3.http://www.moddb.com/mods/occupation-source
4.http://www.moddb.com/mods/zombie-master
5.http://www.moddb.com/mods/half-life-2-wars
6.http://www.moddb.com/mods/shotgun-sunrise
7.http://www.moddb.com/mods/frontiers
8.http://www.moddb.com/mods/half-life-2-capture-the-flag
9.http://www.moddb.com/mods/smashball

-----------------------------

Part1 RAVENHOLM
Part2 EYE OF THE STORM
NO ESCAPE!