Gengar is a real fan favourite and always makes for a brilliant card
The thing is, Gonti supports theft, even when opponent's do the stealing, so this can turn into more than one treasure per turn at the right table
Flareon, Vaporeon, and Jolteon have been regularly added to new sets and hold a nostalgia factor similar to Charizard
Even when retired, Radiant Greninja will have plenty of nostalgia behind it to help it grow in value, especially for mint-condition cards that never saw play
In reality, since they don't have haste, the clock is easy to understand and it's easy to gauge the safe zone, but you still get attacked quite a bit
Graveshifter Graveshifter is identical to Gravedigger except for being a changeling