The way to celebrate a victorious MMORPG boss fight is with a bathroom break and emotes. Square Enix created a couple of emotes in Final Fantasy XIV that would fit the occasion. You can make a female Hyuran clap her hands, dance in a circle or cry to mourn the death of the monster.
I did that a few times while playing Final Fantasy XI just to confuse my party. I think I’ll go with the slugging motion in Final Fantasy XIV.