Whats the anti-torque mechanism in horizontal take-off aircraft? In most helicopters there is the anti-torque tail rotor to prevent the body from spinning in the opposite direction to the main rotor. 
What's the equivalent mechanism in horizontal takeoff single engine propeller, and jet aircrafts, where the air or the jet coming out back from the turbine or propeller is spinning and will cause such aircraft to roll?
 A: If you place two engines spinning in opposite directions equidistantly from the center of gravity, the torque is cancelled.  Hence the old Air Force song:
"Don't give me a P-38, with props that counter-rotate
They'll loop, roll and spin but they'll soon auger in
Don't give me a P-38!"
Single engine planes can compensate with  a bit of rudder . Check  Martin Beckett's answer below.
A: The motor does exert torque on the fuselage.
The pilot, without having to think about it, compensates by applying right aileron, which has plenty of roll authority.
There's more to it.
When a propeller-driven plane is taking off, it has a tendency to yaw to the left, and the pilot automatically applies right rudder to compensate.
That left-turning tendency is due to the propeller descending on the right hand side, at a higher angle of attack (thus more thrust) due to the pitch of the airframe, and also because the wind coming off the propeller is a corkscrew flow, and it strikes the left side of the vertical stabilizer.
If you watch this video, you will see how pilots are instructed to operate the F4U Corsair in WW2.
It is recommended to tune in some right-rudder and right-aileron trim when taking off.
It is also recommended not to take off at too slow a speed because it will seem "left-wing-heavy" due to that torque, and more speed means more control authority.
