Can anyone recommend some good old games
on sale that are not available on GOG?
remembering from the top of my head, there are more.
Half-Life 1 too, obviously,
All excellent choices (well, I don't know much about Kohan, I'll give it the benefit of the doubt based on the rest of the list).
Wasteland (must play, really, pirate it if you must, pay for Wasteland 2 to say "thank you" when it comes out).
Titan Quest is probably the ideally implemented ARPG (The Immortal Throne expac is a must, though the base game rocks even w/o it)
Warhammer 40k The Dark Crusade (get Platinum edition so you get access to more factions).
Age of Empires II: Age of Kings (expac was great too)