I can't vouch for the authenticity of this because I got it from another travel web site but since Italy seems to be a favorite, and I can sure understand why, I thought I'd pass this along:

When travelling in Italy if aged between 18 and 25 or 60+, if you show your passport at tourist attractions they will give you 50% discount. They will only accept your passport though, so make sure you keep it safe and keep a photocopy at your hotel.

Cheers, Rose - Los Angeles