I think the last planet NASA crashed a satellite into was Saturn, I think. Their tagline/buzzphrase was “Carpe Atmospherum,” though in the name of God-and-all-that-is-holy I can’t remember the name of the satellite offhand.
What’s more, we’ve crashed satellites into the moon purposefully as a preface to our manned moon missions. Ranger 1, I believe, was designed to gather information as fast as it could as it crashed and was destroyed, which gave us valuable telemetry
JPL got some good data out of it, though, I believe. May have been applied to Cassini, which arrives at Saturn next year.