TNG, The Royale...a lot of people dislike it but I find it amusing and enjoyable. I felt so bad for the poor NASA guy..trapped in a horribly cliched Vegas ganster plot.
TNG, Time Squared...an odd time travel episode but I like it. Am I remembering wrong or was there a plan to have it lead into the following episode and we find out that Q was behind the weird vortex? But they abandoned that idea before settling on the final version?
TOS, The Immunity Syndrome...the space Amoeba episode where Spock goes Obi-Wan feeling Alderaan's destruction before Obi-Wan did. I've always wondered if George Lucas "borrowed" that Star Wars scene from this episode.