oil /gas/arc/incadescent/merc ? and so on 

i personally have a merc vapor gumball on my moms property and its my favorite maybe its because i grew up in the 70/80's and i remember all the green and green/white lights . 

I would have to say the coolest old lights are the gumballs! I would go with the mercury vapor. A close second is the early GE M-250's!

I would go with any pre 1980 mercury fixture especially a 1960s Wheeler Boston open mercury fixture. It's in my room as I type this and I can see it to the left in my peripheral vision ;-) It currently has an early 1960s GE Bonusline BT-28 clear merc which looks awesome lit up. I also remember when California was a mercury lit scene. In the early 1980s when I was still quite young CA suddenly changed from merc to HPS virtually overnight. Argggh.

General Electric Form 109

A Westy OV-14B

Any brand of top-entry gumball with a MV bulb and a cylinder-shaped remote ballast. These were the streetlights of my youth.

Gumballs and OVs. I grew up with them. Maybe throw in some Radial Waves, M250s, and some vintage Widelites. Of course these would be Incandescent and Mercury Vapor. Gosh, I remember when Metal Halide and High Pressure Sodium were still somewhat 'new' technologies. Oh yeah, and the original ITT Yard Light with a Sylvania clear 175 watt girdir frame Mercury Vapor lamp, those were the days! Strange but I like saying 'Mercury Vapor' and I like the way those words look. Oops, little off-topic.

probably an original M-400.

I like those fixtures!