Yeah, centipede was a good one. I remember really liking Vanguard, Atlantis (Which is on its way as I speak), adventure and that Shoot out game. I must admit that without the manual I found Riddle of the Sphinx to be the most perplexing game ever.
I was really young (about 9) when I had my VCS2600, and I had only two games with it: Space Invaders and Defender.
But I remember having played the crap out of them, and Defender is the first game I ever finished. Ah these were the times...
Hey look, Halo on the Pandora!
It's called Halo 2600, made by Ed Fries.
Was a limited time release at a classic gaming expo recently.
You can now pick up the rom here: Halo 2600
Pretty funny actually, though I guess it doesn't count as an official retro Atari game