I can't think of any par-6's I've played but.......I have played cross-country golf a few times.
For example, I know a lot of you have played Cruden Bay. Well one summer evening many, many years ago some of us of then youngster-ish age reached the 13th tee but realised we weren't going to be able to finish all 18-holes before it got dark, so......we all teed off on the 13th and then didn't putt out until the 17th green - we couldn't have to got to the 18th green as it was pretty much pitch black by then. If we played onto the wrong green or tee we moved the ball to the side, otherwise it was play it as it lies, which made course management and strategy important. Fortunately there was one of those rare occasions when there was no in front of us and no one else around generally, otherwise it would have been a bit irresponsible I guess, but then again....!
I reckon TOC at St Andrews would be a good location for cross-country golf tournament - only 2 holes - tee-off from the 1st, putt out on say the 11th, tee-up on 12 and putt out on 18. Now, does anyone happen to have Mr Dawson's 'phone number - only joking Peter!
All the best