Half Life 1. It's a classic because it legitimately is an outstanding game.
It's good, but it's also legitimately dated at this point. I was playing it last year, and I had a good enough time with it, but not good enough to bring me back to finish it. It's one of those older FPS games with a great story BEHIND it, but hardly tangible in the gameplay. It's just a bunch of going from point A to point B shooting things, with very little narrative.
It's still worth playing if you're a big fan of shooters and don't mind dealing with fairly dated gameplay and graphics, but if you aren't... I can't say I recommend it highly.
Dredd's been in a bundle already, an Indie Royale from a while back.
I want Sniper Elite V1 but... GetGamesGo sucks. I'll wait for another sale.
Indie Royales don't count, man.