I've gained the reputation of a Killer DM who is not out to kill you. It simply happens when you are stupid.
My first kill was with a ceptic ooze. The party barbarian got himself engulfed (actually the whole party did) and died. The rest of the party, well one sold his soul to a deity (who decided to save one of his friends as well) and then the druid eventually escaped the ooze and ran out into the streets stark naked just in time for the ooze's special ability to activate and cause him to go crazy. The guards put him down after that.
Not a very good first kill in my opinion but I have nailed home the lethality of some games with early kills, for instance killing the party cleric in the second session via flaming troll, the barbarian a couple later by hill giant, the crusader with five level 1 warriors. I enjoyed these. I've personally found that I dislike killing PCs who have fleshed out stories and more to tell. Otherwise...well I enjoy it even if I don't aim for it.
Edit: Because I just read the post directly above me the barbarian who was devoured by the ceptic ooze was named Cet and he was a blacksmith.