What a wonderful thread!
Steve's right, of course, the Star Trek theme does have lyrics. One of my favorite recent discoveries was that the original Dick Van Dyke show theme had lyrics. Good ones, too, written by game show favorite Morey Amsterdam. They sang the song (a couple of times, actually) on the TV Land Awards a while back.
Swinging interestingly back on topic, several of you have a copy of a CD I compiled that I called \"There Were Words To That?\". It's a collection of game show themes that you wouldn't necessarily think of as having lyrics. Some were obvious, even to non-game show fans (\"The Start of Something Big\", \"Hooray for Captain Spaulding\") but some were pretty obscure. A Chuck Barris single called \"Lovee\" is the theme to The Gong Show and -- my personal favorite -- it turns out that the well-known Newlywed Game theme was originally a pop song Chuckie Baby wrote called \"Summertime Guy\".