When I learned about the Seinfeld tidbit that they tried to add nonsense lyrics to the theme but failed, I started thinking about theme songs over the years that stick in your head despite the fact that they're presented without lyrics. There are more shows than you think that fit into that category, and they're not all one-hour dramas (where most lyric-less theme songs can be found). Adam put up a list of them in December. But there are particular ones that have adhered themselves to my cerebral cortex to the point where I probably hum them in my sleep:

(Click on the name of the show to hear a sound clip from each theme)