I'm a killer DM.
I've had several TPKs over the course of my 3.x career - in fact my players rib me about it a fair bit because I've committed the egregious sin of TPKing the party
the very first encounter of a new campaign. And I've done this
twice now.
At least one of those particular situations was Mulligan'd (started over, well, skipped past actually).
Other times, if there's room or an area of the dungeon that fits for it, I'll opt for the Total Party Capture (TM), i.e. the "you wake up in a jail cell" maneuver. Alternately I've done the "Wake-up stripped and naked" victim of a monster-mugging ploy.
I get really embarrassed and apologetic when it happens, but my players are nice. For the most part, they seem to appreciate the fact that I play my monsters hard and smart and insist that I run a pretty damn exciting game. In return, they've developed some
extremely sharp counter-tactics and work really well as a group together (and there's been some occasional min-maxing and munchkinning in response as well, which is not so good I guess).
The fact that my players have gotten really good has actually put me in a tough spot as a DM on occasion to match their tactics and keep things exciting (there's only one of me, and sometimes monster powers can be complicated and hard to keep track of!), so yeah, there's been a little bit of an arms race going on in the past.
But it's a hack-and-slash gaming group, and it's the way we roll, baby. If we were to try a more narrative/story-based campaign, I'd probably cut back on the ruthlessness a bit.