Tactics has my favorite ending. The scene isn't spectacular, but the ending itself was great. One of the villians (well, technically a villian) becomes king, the corupted church gets to continue, Olan is killed for telling the truth, Balmafula has her tongue cut out, and the heroes had to spend the rest of their lives in hiding. Much more realistic than the others.

As for the worst ending... Hard to say. FFI, I guess. You kill Chaos, and then there was just some stuff about returning to the past, and then THE END. I didn't like that. But then I didn't expect anything grand either.