(Thread prompted by the V4 Capri in the other thread, ‘cos a V4 is one I still need)
(And I just mean engine cylinders, getting into drivetrain configurations will be a total rabbit hole)
Single - a couple of Husqvarnas
Flat twin - 2CV
Flat 4 - Beetle
Inline 4 - loads ! Currently The Compact.
Inline 5 - VW T4
Inline 6 - various BMWs
Flat 6 - 911
V6 - several, currently The Scimitar
V8 - several again.
V10 - Touareg
V12 - Q7
I did my motorbike test on a CB500, a parallel twin, so at a pinch I’ll claim that too. I’m certainly not going to buy one

Without going into real rare / exotic (straight 8, flat 12, anything at all >12) I think I’ve almost done as much as I can. I want a VFR800 to check off the V4. There’s no V-twins I fancy. And a Bentley Continental for the W12.