A Beech 18 really does have it ALL. Multi, Radial engine, tailwheel bush(ish) plane. What more could you ask for. The Cessna T50 Bobcat would also be acceptable, but they're quite scarce.
Beech 18s are very cool, but if there is one airplane that really requires a pilot aboard, well, it’s the 18. They say you just start to figure out how to fly it at about 500hrs., and at $500hr to run, it will cost you a quarter million to get comfortable in it. Once airborne, the Beech is a delightful flying airplane, light, ball-bearing controls, easy instrument platform, and will carry enough ice for the happy hour, but from short final on, it requires a whole new level of centerline consciousness. Not particularly hard in a crosswind, hard all the time! Got no tail wheel steering, just taxiing to the runway is done with a mysterious combination of differential power, brakes, tail wheel lock and when on the runway, ailerons. When you first fly it, you’ll want to take it to Edwards, so you’ll have enough runway, but a skilled pilot can work it out of a narrow 2500ft strip. It’s considered the heaviest light twin: a Cheiftain weighs 7000lbs., a C-404 weighs 8450, but a high cabin twin Beech 10,200lbs! Think of it as a 10,000lb. Piper Apache - when it’s heavy, if you lose an engine below 3000ft. you better do everything right or you’re gonna die. I’ve got 5 type ratings, and have flown a few airplanes but I consider the 18 as maybe the hardest of them all. Maybe single-pilot Merlin IIIB (without autopilot) would be harder IFR.