I currently own these:
Tempest
TRON
720
Dig-Dug
Ms. Pac-Man
Pac-Man (cocktail)
Mr & Mrs. Pac-Man (pinball)
Marble Madness (PCB and control panel swaps out to other System 1 games like Peter Pack-Rat)
Neo-Geo 4-slot Japanese "sit-at" cabinet (I also use this for JAMMA PCBs)
Spider-Man (I use this for 4p JAMMA games, mainly beat-em-ups)
STUN Runner (sit-down)
I've once owned, but later sold, these:
Joust (though I'd very much like to own it again)
APB
Asteroids
Arkanoid
Moon Cresta (cocktail)
Omega Race (cockpit)
Victory Road
Race Drivin'
Spy Hunter (cockpit)
And I'd really like to someday own, among others, these:
Libble Rabble
Robotron 2084
Crystal Castles (greatest cabinet in history)
Drummania / Guitar Freaks
Point Blank
Medieval Madness (pinball)
Funhouse (pinball)
Though I must say that the novelty of tracking down, procuring, and painstakingly restoring these beauties has largely worn off, and now I'm left with a whole lot of space taken up. Hopefully one day I'll have a big house to keep them all in, so it won't seem like such a burden.
As for suggestions, I'm with Drohne. If you only want to have one cab, invest in a nice JAMMA cab and then pick up various PCBs over time. Getting a cab like "Run n Gun" is largely worthless, considering that the PCB alone likely sells for about $20 and that the cab itself is nothing more than a generic box with some ugly stickers from a kit slapped on. You'd be better off buying a generic Jamma cab and finding the PCB on its own.