If I haven't fired you yet, it's because I'm still firing your mom in bed.
I was an automatic difficulty skirmish whore, and I got mine pretty freaking high (I forget the exact number, but practically twice the Legendary difficulty) by using Cutter and rushing with Vultures and using ODST spam as backup. On one occasion, though, I got the bright idea of doing a 3v3 on I believe 164 difficulty. I rushed like usual, but was repelled by the combined enemy just because they HAPPENED to be converging in the area I attacked.
This single battle spawned a six hour skirmish. And I won. At first my side was doing well but then my AI pals started to lose, and it went 3v3 to 2v3 to 2v2 to 1v2, and that's when it started to get tough. I thought about giving up multiple times, but I just kept up the Vulture spam. I tried using counter units, but the time and effort I used just to get different units started made me start losing, so I had to revert back to mass Vulture spam to get back to a stable point despite the almost overwhelming number of Vampires.
I think I either got lucky, or one of the enemies tried something different as a response to me trying different units that got them. I managed to get one base more than before, and started up another two vultures. While they were quickly getting back that one base, I crippled their military output bases and after that it was all downhill for them.
Six hours of trading blows, back and forth, and I came out on top. Never before have I felt more satisfaction and pride.
[Edited on 01.04.2013 11:53 AM PST]