The many sieges of Anacan when it took the enemies of the Antoza Commonwealth three attempts and the combined host of eight or nine realms, which was basically everyone else on FEI at the time. One of the sieges of Anacan (the second one I think) still ranks as the second biggest battle ever in BM history.
The sack of Giask during the First Lurian Civil War. Not a particularly big battle, but it was epic in the sense that it was a complete surprise attack on an enemy capital, basically ending the war in one blow.
The Viking raid in Eston during the Viking Wars. Norland and BoM combined forces to launch a devastating raid on Eston's lands, forcing Eston to sue for peace.
And a personal moment I'm proud of:
the Mansbridge Massacre.
