I love opening and closing credits. This probably stems from my love of film scores, as in older films, the main title and end credits gave you a chance to hear the score without the talking and noises that would accompany it during the film itself. Nowadays, with the distinct lack of opening credits (which I've already complained about), and the rampant abundance of songs over the end credits instead of score... well, lets just say the art of opening/closing credits is dying. And I hate that, passionately. Right up there with bouncing cameras, choppy editing, and stupidity in plots. They're ruining my movie-going experience.
Before 1970: Opening Credits - Okay, this is nearly impossible to choose from. Most old movies had great opening credits. Great themes and theme songs. There's the straight-forward ones that have something cool about them (Kiss Me Deadly - Nat King Cole song and credits flowing backwards as we head down the highway), or there's crazy, clever ones like Mad Mad Mad Mad World, or cool funny sung ones like The Court Jester, or epic ones like Ben-Hur. I loved when movies had overtures. Opening credits were an art in the old days.
Post 1970: Opening Credits - Big Jake (1971). Music by Elmer Bernstein, and a really nifty history lesson that sets the background for the movie. The juxtaposition of modern advances and civilization with the violence still going on in the Old West sets the perfect tone. And always makes me realize 1909 wasn't that long ago, really. These opening credits just make me smile.
But since 1971 is so long ago, I have to mention The Untouchables (1987) again as well (with Dead Again and LA Confidential right behind it, and on the clever animated level: Catch Me if You Can), because The Untouchables still fulfills everything I want out of opening credits: mood-setting score, nifty visuals, and actual credits where I can see who's going to be in the movie I'm about to watch.
Before 1970: Ending Credits - Well, this is harder, because there wasn't much to end credits in the old days. "The End." Occasionally a cast page after that as time progressed. And I have to admit, I loved that too. As for a favorite? For funny - The Road to Bali, just to watch Bob Hope struggling with that "the End" sign. "Oh no you don't!" For serious, In Harm's Way (1965) would probably take the prize from me. Those crashing waves, that very ominous but amazing end cue from Jerry Goldsmith. Gives me chills every time.
Post 1970: Ending Credits - for fun, A Life Less Ordinary and its wacky claymation is highly amusing. For serious, Star Wars. Those last notes of the movie, segueing into the end credits ... bliss! And it's a prime example of a film of where I settle back into my seat during those end credits just to hear the music.