List of hard to find/rare vehicles?

[Vipes]

I only know of three:

Salem - Zin Tower
Relic - Airport
Genki Car - MOM Hard, rare spawn in areas

 

[Reaper4911]

i just saw the Genki car in MOM but I was trying to get a good time so I blew it up.

 

[Bring the Noise]

The Genki Bowl (Quad Flamethower) is added to your inventory as part of a side quest or objective completion (can't remember I've been up to long and I'm about to go to sleep).
You also end up with the Manipolt, and the Genki Girls vehicles (or I did).

The one I haven't come across yet is the Monster Car that was in the E3 footage...