Just played Chrono Trigger. I'll be playing that again until I get better at it, knowing all the grind spots, learn all the best combos, and get all the endings. Or most of them, anyway.
Also, having just played the English version of Mother 1, I'll play it again soon so that I can learn that as well as I know Mother 2/Earthbound and Mother 3.
Oh, and that part of the Co-op portion of Portal 2, the one that requires no deaths. Since I intend to do that, me and my friend are gonna have to learn it inside and out.
As for games I've already played many many times...Paper Mario, Paper Mario: TTYD, Earthbound, Dragon Age: Origins, Ocarina of Time, Twilight Princess, New Super Mario Bros Wii, Gauntlet: Dark Legacy, and Baldur's Gate: Dark Alliance 1/2. And Just Cause 2, if that counts, since there's only so much to do, and as soon as you learn it you'll know it anytime you play. 89% and counting...