One FPS that I know of that is excellent for LAN parties is Unreal Tournament 2004. Source: my own personal experience with the game at LAN parties I used to frequent.

One of the funnest mods/maps are the what I call Lazer Tag mod (everywone gets a lazer that kills in one shot :D) and the maps that were made to be a living room but really huge. Good times were had when you could run under a couch, hide in the dark space underneath, and just shoot at anyone one shotting them :D. Fun fact: the way the map was done or whether this was due to how the engine worked, you could hide under an object and remain unseen for anyone outside :D