The only thing that comes to mind was one nasty string of fights where the AI sent about 500+ men (Rhodoks) to siege my newly granted First Castle Ever, and I only had about 60-70 men in total (primarily Khergit) between the castle and my field army. Lured a couple of groups of 50-70 men into chasing my 50 or so, got them far enough from the castle that the other 350+ couldn't join in, and then outran them until the other turned back. Charged the one still chasing, and got to fight an almost even battle of 50+ to about 70 of them. After that, got the second to resume chase, and destroyed that 50+ unit. Had to rest overnight (just about every Companion was Wounded), and then lured a stack of about 120 off to the slaughter (another tough fight, since Rhodoks are hard to take on with a mounted army). By the time my unit recovered overnight from that, the remaining 250-ish enemies (the opposing King and a smaller army) had started the assault. Joined the defense, and proceeded to hold the walls against roughly 4 times my number, foregoing lance and shield to load up on a bow, double load of arrows (I still ran out), and a sword. I think I gained two levels in that mess, mostly from archery in the castle defense.
Mainly memorable because it was the first campaign where I got a castle, and the opponents almost immediately tried to take it from me. I wasn't about to let it go.