I recently re-watched all the original Star Trek movies, and was pleased to discover that Star Trek IV: The Voyage Home held up beautifully. I remember seeing it when I was a kid, and thinking the whales were cool—and boy, they still are. Here's a blooper reel from the shoot, including plenty of flubs, jokes, and Shatner/Nimoy goofery. (Note that Nimoy directed this one, so he seems to keep the camera rolling when he's enjoying how far off the rails a scene goes.) Behold:

If you want to binge on the movies, there's a nice Blu-ray set, or they're on Netflix (here's The Voyage Home—streaming!).