Half-life 2 Ep. 2. I just couldn't be bothered to fight the horde of annoying hunters and striders. Only ever finished one GTA game, Vice City, but made it to the third-to-last mission of San Andreas twice, only to give up 'cause I'd lost interest. STALKER: Clear Sky; I finished the first game with the "proper" ending, but Clear Sky just irked me, with the "Beat 200,000 bandits with your shitty pistol while on a timer and in a fopping swamp".
Other games: Prince of Persia: Sands of Time (my laptop on which I was playing it was stolen, and I never bothered to install it again), Neverwinter Nights 2 (bad gameplay, especially compared to NwN1) and Max Payne.
):