The Skyliner SSTO is the latest and greatest in the KCS Badger Works line of spaceplane cargo lifters. This remarkably sleek looking craft can haul four kerbals and up to 36 tonnes to LKO and return to the runway from whence it came, and the best part is that you don't even need to wake up a pilot and nurse him out of his hangover to do it (I'm looking at you Jebediah), thanks to the CH-J3 Fly-by-wire avionics hub. The Skyliner is extremely stable in all flight regimes and maintains aerodynamic stability regardless of how much fuel you have, which is probably a good thing, since all the pilot kerbals are now on strike to protest the loss of their jobs. Warning: do not exceed 36t cargo mass*, warranty void if used as ICBM.
Download from KerbalX here.
*the RCS system is fully capable of de-orbiting the vessel should you find yourself sans fuel in LKO after delivering a heavy cargo