The kill that pleased me most was during the big endgame fight in the burning city against the mindflayers, absolutes and goblins. (So we're all lvl 12 at this point)

Note, I prefer the RP and am not a specialist in fighting, so every big or boss fight on balanced mode is a big challenge for my party to survive. So it may not be a big deal for the experienced honour mode fighters.

Gale had cast a cloudkill on a region containing a few enemies who died in the next two turns, but there was still a sneaky way to get around it apparently and an inquisitor of the absolute (95 hp) managed to get up the rampart and arrived in front of the cloud.

My lvl 10 bard/lvl2 warlock threw eldritch blast at her. That flung her into the cloudkill and killed her completely. I don't think any of my PC ever did so much damage to an opponent in one action. It felt so good.
(I love that class combination by the way.)

The stupidest kill was on my sweetheart shadowheart. I thought I was targetting the enemy next to her, but then it turned out I blasted shadow. Yea, when the fighting is intense I get stressed sometimes and do surprisingly stupid things.