I love the Beech 18. Just the sound of it starting on the ramp is a treat for the ears:
Hard to go wrong with two R-985's. Superb engines. Great sound! People ought to pay you, to make it!
Remember to lock the tailwheel before takeoff, and you need a left brake. Or so my best friend told me.

My fetish aircraft would be a Twin Bonanza. Everyone hates them, but those geared Lycoming GO-480 engines make a truly orgasmic sound:

If that doesn't give you a chubby, you have no soul.
EDIT - continuing on the topic of completely impractical fetish airplanes ...
Twin GO-480 Lycomings may not be a popular configuration these days, but I loved them as pushers:

That needed to get from Brantford to Belize in a hell of a hurry, where the retired AC pilot had shacked up with the nanny, who smoked too much.
Saw it tied down at Chetumal, later. Funny, running across old friends like that.