Some favourites for me are
Skyrocket (Bally)
Centigrade 37 (GTB)
Lady Luck (Williams 1968) .. I have one of these .. pretty unique .. playing blackjack and trying to beat the dealer while also trying to beat high score
El Dorado (GTB) .. I have one of these .. lots of drops and they reset when all down !
Gulfstream (Williams).. I have one of these .. Tic Tac Toe on a pinball .. trying to light all 4 corners for 3 specials is pretty impossible