I'd have to rank mine in two categories.

Old school, 1 is WH2O, i've owned four and it's almost always been in my collection, always traded up. I know the rules and love the ramps. 2. BSD, same as before, always traded up, love how brutal it is. 3, FT, same as before, owned it four times, always traded up. I love the theme and cheesiness, plus the simplicity but difficulty of it. Honorable mention, NF, had it four times and always traded up, love how fast it is, no pops, magnet ramp. Was almost always in my collection and was the last to go when I got out of the hobby a couple years ago.

Fast forward, I got out of the hobby for the past four or five years, catching up on "new pins" I've never had. Iron Maiden Pro is number one, love the shots, theme, four flippers, music, ramps, orbits, all of it. Number 2 is MET Pro. I've played this on location ever since it came out and always wanted one, it's brutal, I love brutal pins, had to get a NIB one, just got it a couple weeks ago. Number 3 is TWD Pro, again, played it on location since it came out, always wanted to own one, love the theme, TV series, difficulty, deep rules. These are my three current keepers in a six pin max collection. Honorable mention, Munster Pro, please update the code, I love the theme and playing it, but it's almost too simple.