The NEAR spacecraft was designed to visit a few asteroids with the main target being one named Eros. This probe was meant only to orbit this object closely for a year… and it did. But as the probe ran out of feul and for lack of any reason not to, the controllers decided to attempt an impromptu landing on the surface. Even though the probe had not been designed to do this (it lacked landing gear of any kind) they managed to “rest” the probe carefully upon the surface in 2001 and it continued to transmit information back to Earth for more than 2 weeks from the surface.
Image Note: The color of the asteroid itself was enhanced to match that of the close up image included in the upper right. The original full image was black and white.