Well mine is going to be a bit boring and not much controversy as my top 3 are all popular machines.
Much as I love my Hardbody when it was working I only liked playing it for 15-40 minutes at a time.

1: Iron Maiden Prem:

The pin is a dream theme for me. Seen Maiden 6 times live and I own all their albums and most of the bands solo stuff. I think the layout is a very unique layout, while also just having enough of the traditional fan elements to make sure the game flows and shoots great. Some unique layouts can feel gimmicky after awhile. This always feels fresh and fun to shoot.
So many different strats and ways to attack the machine. You can also alter and change your strat depending on what you've accomplished or still need to.
Games rules are amazing, great callouts, decent animations(some really good), and for me the best damn music on the planet.

2: Elvira LE

This is the pin I am currently playing the most of. The rules are not there yet. Still a lot of fun to be had. Love the videos(i do skip them from time to time), love the movie clips. Just a lot of fun to be had playing this game. Its a nice layout, and doesn't get old shooting it. Also a lot of really cool mechs on the playfield. So far there is a couple of different strats you can use. But, mostly it revolves around setting the same stuff up. Like... Get a deadhead to bash. Lock 2 balls in the garage. start a mode. Start mb and try to complete the mode.
Once you complete the mode and are out of mb.
Unlock house, get mb ready again. And try to complete the mode. There is strat to know when to just go for modes or locking balls, and when to finish off the deadheads. 2 completed modes gets you an extra ball, 2 vanquished deadheads does the same. So that should be the focus for a casual game. Also want to make it to house party. The modes themselves are also good to know when to go for. Teenagers from space is easiest to complete. Then I think its Night of the Living dead. The rest are harder and take more shots. So those tend to be the ones I go for. But, I might do teenagers before I start mb.
As I said. Having a blast playing this one right now. Its really the only pin that I've been playing for the past 3 months.
When the code is finished it could move up to number 1... but, it be tough. I love Elvira, but I love heavy metal and Iron Maiden more.

3: MBr LE

I love this machine. Its a lot of fun to shoot .And I've found that the only thing more dangerous than Dracula's bite is his dang feet!!!!
Won't bore you all with what I like about this one. Just the fact that I had no desire in owning a MB... I mean I thought, one day would be nice to own one, it is a classic pin. But, there were dozens of pins I had on my to buy list over this one. Then I went to the Chicago Expo and I saw this one and I fell in love with it at first sight. It looks amazing, played amazing. Loved the animations, the callouts, the gameplay. Thought the LE was one of the best looking pins I ever saw, and I knew I needed to own it. And so I bought it. And I love it.

Honorable mention goes to my beater Sinbad. You put some tunes on and I can play that game for hours on end. Just a really fun machine.