Junkyard - only played it on location a few times but I really like it and almost bought one about a year go (backed out because price was a bit high compared to the things I had to fix on it). I plan to own one sooner or later. The theme is great and the wrecking ball toy is very unique. I know some people don't like this game for the interrupted "flow" (like the "shoot spike" minigame") and such, but that doesn't bother me at all. Also some think the playfield is rather "empty/open" and nag on it because it doesn't have any pop-bumpers, but nothing of that bother me at all.
Revenge from mars - The first pin I bought and had it for about 3 years. It's fun, lots of comical call-outs and the theme is good. I did like the pin2000 system, robust and had 0 problems with it, but at the same time the pin "form factor" stood out between all my other "normal" games and it was what got me to sell it in the first place (simply didn't fit in physically with the other games).
Roadshow - Underrated and fun game. Not that expensive too (compared to many other 90's B/W pins). It's a lot of pin for your money being a widebody and two talking heads. Have one in my collection and so far no plans on selling it. If you get one, make sure to installe the latest "official" game ROM from Soren, it will make the cities you travel through more random and the game gets much more enjoyable (less linear).
LoTR - played it many times on location but honestly, It's not really my cup of tea to own one (I get bored of it rather quickly each time I play it). I know "most" people like it so I guess it have something I fail to appreciate, dunno. It's known for loooooong ball times (if you're a decent player).
Flintstones - Also underrated and on my "pin I want to own someday" list. I like the theme and the ramps returning the ball to the opposite sides is a fun thing I never get bored of. Probably a keeper if you bought one.