This is such a tough one for me, I've spent all day ruminating on it. And I've decided the niftiest opening credits I can think of are for 2006's Casino Royale. I love the somewhat retro feel to them, which is appropriate for a reboot of a franchise that began in the 1960s. And I love how the cartoon characters shatter into card markings -- it's just nifty. Instead of describing it, here, just watch it yourself if you want:
As for best closing credits... they may not be the best, but I love the funky claymation closing sketch during the credits for A Life Less Ordinary (1997). You can watch them here on the animator's website.