Can't say it's my proudest moment, because most of those have been pushed to the back of my mind and distorted beyond all recognition, but one awesome one came last week.
I was playing Age of Empires 3 with five friends at university, it was a free for all on New England. I was as far away from the water as possible and so disadvantaged resource wise. After peeing off everyone with a cavalry rush to take out villagers at the start, everyone decided to forget it was a free for all and attack me (this started about 40mins in).
About 2 and a half hours of them bashing me, I was still alive, only two of them remained (and they were pretty much gone). We had to go to a class, but the breakdown of the scores put me in the lead with ~2k points, with second place on around 1.2k points.
I felt I accomplished something that day - mainly epic bragging rights towards each of them.
Oddly, we haven't played AoE3 since then.....
Epic
I recall doing something similar with my mates and AoE2. I haven't played it with them since either! >.<
