Oddly enough, the movie for which I best remember him came out a couple of years ago. The movie was Bubba-Ho-Tep. In it, he played an old black man living in an East Texas nursing home who thought he was JFK. (According to him, JFK survived the assassination and "they" replaced part of his brain.) He teamed up with Bruce Campbell (as Elvis, who, as it turns out, had switched places with an Elvis impersonator in order to escape the aggravations of fame and had not been able to switch back before the impersonator died at Graceland) to fight a soul-sucking Egyptian mummy that was preying upon the residents of the home.
Yes, it all sounds very silly, but, believe it or not, it really wasn't that silly at all. I remember going to see it in Chicago in 2003 at the theater (unfortunately missing by just one day the chance to see Bruce Campbell in person at the premiere). It was actually an excellent movie that deserved a wider audience than it got. Bubba-Ho-Tep successfully alternated between horror, drama, and low comedy. Permeating the entire film was a surprisingly effective elegaic sense of regret for what might have been, a feeling that we all share from time to time as we grow old. The ending was surprisingly moving. Ossie was great, alternating between being funny and moving, often in the same scene.
I'm going to have to go back and check out some of his older films now, ones I haven't seen before.