What is something you have always wanted to do in KSP but have as of yet to do?

Ever since I first installed the game in 2014, I've wanted to do a Duna mission in science or career mode. I always restarted before doing it, but this install seems to be keeping my attention a lot longer. I've already done a landing on Asclepius (a modded planet between Kerbin and Duna's orbits), and flybys of Eve and Duna. All I have left to do is refuel the interplanetary vessel and attach a lander, but that will still be a week or two of work.