For me there was a weird soviet game from a time immemorial. I happened to find it while browsing an ancient PC (think BEFORE Pentium I), and it was about some funky character that had to cross a river by jumping on circles of various sizes that shrunk in time and moved around. Never managed to finish it, I was always getting to a point where there were no more available circles around. Oh, and the game crashed each and every single time, and only a cold restart would disengage the game...
