I have been lucky enough to have 2. The first was August 26, 2006 at Seaforth Ontario, Canada, where I had been a member for several years. The 5th hole is a par 3, with a creek running in front of it, 135 yards. I was playing with my a friend, and I hit a 5 iron and watched it disappear. 2 of the grounds keepers who were also my friends were working on the green and they had stopped while we hit our tee shots. The interesting thing here was that 6 days later, my mom hit her first and only hole in one on the same hole.
My 2nd one came last year at Foxwood in Kitchener, Ontario on 2 red. On Oct 21, 2012, I was playing with my regular Sunday group of 3 other guys. It was cold at 8:30 in the morning, and with the ball not carrying, I hit 5 wood 145 yards completely over water, that bounced once and stopped. We could still see the ball from the tee. For the next 10 minutes, my partner and I recount all of our hole in ones and near misses. Turns out my buddies' family has hit several hole in ones on the same course in years gone by. At this point, we both think that the ball is beside the hole and not in. Turns out, the flag was holding the ball up. When we got up to the hole, and moved the flag, the ball fell in. Sweet.