I would like to start a thread here to collect C64 programs that have been successfully tested in the C64 mode of the MEGA65.
That means that you really tried them yourself in Xemu or on the DevKit/MEGA65 and didn't just hear them "from the uncle of the brother of your neighbor".
I'll start with Colossus Chess 4. I copied the files with DirMaster to a D81 image and was able with it to play a game successfully in C64 mode. The start screen looks a bit "chaotic", but the game itself works fine (you use cursor keys and return to move and confirm your pieces and moves).