@Greg @brennen @keithzg @packetcat Worst one I saw was Sister Machine Gun's "Burn" album, where they hid an entire track at the beginning of the album in the pre-gap area. You literally had to have a CD player that could understand a Track 0 and go backwards into it.
I have one CD player that can do it. Very few can handle it.
Honorable mention: Fell Venus' @ album, which had silent tracks and then silence at the beginning of a track.