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Fighter Aircraft, WWII-ish

Top speed ~190m/s, which I believe to be the maximum for single-engine propellers and very comparable to several real-life aircraft.
It handles like a real prop aircraft, that is, overly complicated and requires some getting used to.

This craft is not supposed to be any specific real aircraft, I just wanted it to handle as realistically as possible, and for it to fly as fast as possible. Nonetheless, there is definetly some Thunderbolt in there, some FW-190, and most definetly some Corsair, due to the propeller torque making takeoff ... rather interesting.

--- On Propeller Aircraft ---

It took me quite a while to figure out how to get the maximum performance out of a propeller, so let me share the secret with you:

The blades of the propeller need to be at a certain angle to produce thrust; If the angle is to steep, it won't produce enough thrust, but if the angle is too flat, they have too much drag.

This angle depends on the crafts current airspeed (the faster the aircraft, the higher the angle), so you need to adjust it constantly for optimum performance. Since KSP's physics don't like it if you place servos on the rotor, this is accomplished by deploying the propeller blades and mapping their authority limiter to an axis.
With some careful adjustment, this also allows for reverse thrust, simply by un-deploying the blades via key binding.

So: While Propeller RPM is still mapped to the main throttle, it should remain at maximum;
Airspeed is controlled via H/N, to take off increase prop angle in steps from +70 to +140 for up to 190 m/s (neutral thrust at +66, having one of the blades' part action menu pinned to the screen is a must!)

This might take a little getting used to, especially since overshooting the optimal angle will also slow you down, so you might need to decrease it occasionally. The torque of the single propeller is balanced out by two flaps, these will also need to be adjusted to your current airspeed with J/L.

(sorry for the essay, but I had to share this, since I've seen many people getting ... less-than-optimal results out of their propellers, and this should help a bit)

--- tl;dr ---

Or you can just say "screw all this fiddling around" and keep the default settings, which will get you 130m/s with decent manueverability.

1 - Flaps
6 - Reverse Thrust
0 - Toggle engine
Throttle - Engine RPM
H/N - Blade angle
I/K - Trim pitch
J/L - Trim roll
Stage - Bomb
Abort - WEP, +50 m/s