Hey, there's a beta mod (single-multi) for HL1 called: "Robotech-Invasion", the SP story is kinda short and the MP comes with only three maps (coop). However, the mod itself is beautiful and features new textures, player models (manga related), lots of new weapons, new sounds, etc.......
http://www.planethalflife.com/espacemod ... ch_sp.html
HL2 is now out, and this mod project might be dead..... Anyone knows about the final version of this mod????