My favorite item(s) in all of the Mario games is/are...
Item (game it's in)
Fire Flower (SMB, SMB3, SMW, SML, SML2, etc.)
Star (SMB, SMB2, SMB3, SMW, SML, SML2, etc.)
Metal Cap (SM64, SM64 2?)
Wing Cap (SM64, SM64 2?)
Vanish Cap (SM64, SM64 2?)
That's about it...
Mario Maniac!!