The funny thing about MP3 players is that it makes you see things in a new light. I put some tracks on mine last week and then hadn't used it for a few days - today when I did play it, it was interesting guessing what the track was. Another thing that I notidced was that the intro to "Stupid Girl" by Garbage was almost identical to that of "Train In Vain" by the Clash (can anyone else verify this I wonder?). It's only the first few bars but when it came on I really thought it was the Clash track (bearing in mind it's also one of my favourite Clash tracks of all time!).
The other thing that struck me is that there some bands where you only have to hear the opening bars of any of their tracks and you instantly know which band it is (you don't need to wait for vocals). Two that I can think of straight off are Coldplay and U2 and I am sure there are more (I am slightly tipsy as I write this so bear with me!). Usually it is a certain style of guitar playing (the exception being Nirvana who nearly always start with an unmistakable bassline).