Originally inspired because I just listened to "Sakura Saku." Although it's not restricted to anime by any means :).
If you've got one, please post a link to your favourite theme songs! Games, tv shows, whatever. I'd love to hear them, and they'd probably end up giving me some wicked nostalgia too.
My favourite version :).
I have plenty more favourites, but I'll let you post some first :3.