I once launched a Venture star without cargo, and used the remaining fuel to go to the moon. Once my translunar trajectory was perfect, I didn't have any main engine fuel left. I used RCS fuel to get a lunar PeA of zero meters. I approached the surface while still in a hyperbolic orbit, and used the landing gear to try a smooth landing. The smooth touchdown was a succes, but it bumped me up, and the RCS was not strong enough to push me down again. I managed to do a retrograde burn to get into an elliptical orbit, and do another touchdown in an attempt to slow me down for a final landing, but the RCS fuel was empty before I could land.
I also tried to use a Delta Glider with unlimited fuel to push the ISS towards Mars. I didn't really have a flight plan, but I managed to spiral outwards to increasingly larger orbits. Problem was that the thrust force wasn't really pointed towards the CG, so each engine burn made the ISS rotate. All of it was so annoying and time-consuming that I never escaped earth.
I also landed (I mean crashed) on the sun, using a 'realistic' trajectory. I got rid of most of my orbital velocity by doing a 'backward slingshot' around Jupiter, with an extra engine burn at the 'Perijove'.