I currently have 4 John Borg ((pro)) pins which were ~$4700.
While some might say that's a lopsided tilt in my medium size collection, I love them and would be hard pressed on which one I like the least.
While Borg has designed these great pins, we can't ignore how the rules/art/theme/sound/music/dots (etc.) come together and in how the Pinside community has augmented the sound/music in great ways.
One thing in common is they're somewhat simple (on the pro) not a lot of moving parts, but the simplicity is often an asset and the (often) short games with intense moments and big rewards keep me hitting play and on pinball nights these pins are great for multi player games especially since one single shot can turn the tables in a big way.
Met is probably my favorite. While I am not a master or have not got very deep into the back side of the rules. I just love the shots (ramps and loops) as well as the fun in line drop targets, the simple yet elegant captive ball and snake toys. I love the theme, music, rules etc..
Tron not be as intense but is very smooth and the sound/music go along with the rules and love the way SOS is attainable leading to Portal which I've yet to reach.
IM which is so easy great flow loops, ramps and great toy (Monger) and three spinners! Can't get much more simple yet intense.
TWD speaking of intense, this is the one that gets me hitting the tilt more than any other. It's another seemingly simple pin without too much going on (at least on the pro) but yet it does a lot with it's simplicity.
I have owned XMLE and played Avatar a bit. They are both fun but didn't think they were *as* good as the four I currently own. I have only played Kiss once have not formed an opinion, have played BBH but don't recall it very well but the theme was not my favorite.