The most fun XC workout I ever did was during summer training in high school. It's funny because most of what coach had us do was awful, but this run was great. He had us on a grass loop with a few small hills, it was somewhere between 1200m and a mile. The varsity guys there started off together (maybe 12 of us?) in a line and just ran a comfortable tempo. The guy at the back would surge and run to the front then settle in. After that the next guy would go.
I have no idea how long we kept it up, maybe 20 or 30 minutes. People started dropping off about halfway, and in the end we were down to just 4 guys and we were rolling really good. I was not top 5 on our team, but I did make top 4 that day. Something about that style of running just worked for me.