Anatomy of a Murder (1960)
With a fantastic jazz score by Duke Ellington, Saul Bass' already iconic credit designs kicks off Otto Preminger's fantastic courtroom thriller like no other film could.
Dr. Strangelove, or How I Learned the Stop Worrying and Love the Bomb (1964)
The film's satirical anti-war tone is ingeniously incorporated into the opening credits by Pablo Ferro with weird printed writing and setting a romantic ballad over phallic-looking planes. Yes, it's basically a sex scene with jet planes.
Once Upon a Time in the West (1968)
This is one of the longest opening credits in mainstream cinema. Sergio Leone's classic spaghetti begins with a long quiet sequence where you can cut the tension with a knife.
Another classic Saul Bass designed-opening credits which kicks off Alfred Hitchcock's classic thriller. Man, the 1960's seems to be my favorite decade for opening credits! LOL.
Lots of superhero/sci-fi/fantasy movies have showy, spectacular opening (or closing credits) but I think the best would still be the original 1978 Superman opening. It's so great, Bryan Singer copied its style for Superman Returns.