YES! good one, tEAbAG! They Hunger is bloody brilliant. It's the best SP mod I've played for HL. Another good one is USS Darkstar, and Counter-Life is quite good as well - you get CS weapons for the HL single-player game!
Half Life is one of my 5 all-time favourite games, along with FS2, System Shock 2, G-Police (Playstation) and Hidden & Dangerous.
Deus Ex is cool, but ugly ( I just don't like the graphics - sorry)
Another kick-ass game is No One Lives Forever and the sequel. They're funny at the same time as being top-notch shooters.
The C&C series has to be good as well, but Renegade was crap (SP, never played MP), and Ground Control is great.
I REALLY hope it is HL2. Unreal 2 was pretty, but pretty dull, and Doom 3 is going to be more of a 1st-person Resi than an out-and-out FPS. Duke Nukem Forever keeps disappearing, so HL2 is the only real hope for the genre at the moment.