Perhaps the most amusing surrender I've received came in one game where the Eee traded me a commlink for some race (on the other side of the Eee, apparently; I had no idea where they were.)
I called 'em up, asked them to surrender (at the time, my empire was already fairly badass, and I usually play Evil, so hey...) -- and, surprisingly enough, they did.
After that, it may have been just a coincidence but the Eee were pretty angry at me.
*500* ships in a fleet ?!
In my present game, somewhere 'round turn 280-290, w/ ~500 colonies so far (but all the surrendered ones are rioting... it's REALLY tempting to just blow up their planets) and 430B, I doubt I've more than, oh, about 60 warships in total. Probably fewer. But they're VERY nasty max-tech warships -- only one's ever been destroyed, maybe one other battle one sustained minor damage due to carelessness, and 4 enemy AIs have been vanquished so far...
------------------
-- The thing that goes bump in the night