You know, I plugged in 3-4 with the nagging feeling there was another, then I realized, oh yeah! One character got raised from the dead! So 5 deaths, albeit one with a raise dead involved. I'll just keep it at 3-4, though. Heh.
It's a Scarred Lands campaign, currently level 11.
The first death was when an air elemental knocked a PC off of a cliff, sending him plummeting to his doom, at 6th level. He was in the negatives, stabilized, but had tried doing...something, I don't recall what it was, that was strenuous - but would have possibly saved him, whatever it was - that sent him back to bleeding, eventually to his death.
The next occured that same session, because my PC's are gits. I'd had an aerial servant guarding an entrance into a cavern. An NPC stepped into the fray and was killed in one hit. Then the meatshield of a dwarf came in, was hit, and immediately dropped to half his hitpoints in one round. The aerial servant wasn't going anywhere, and I'd made the PC's aware of that. Despite that, though, they kept fighting. So the dwarf died. Only then did everyone else high-tail. Gah.
The next two deaths were in pursuit of an artifact at 8th level. The artifact allowed a Wail of the Banshee. The person holding it did so, when she was down into the single digit hitpoints. Those who died could have lived if they'd stayed away, but all the characters insisted on getting up close and personal, even the wizard, to drop her, despite it being unnecessary. So...two more dead PC's.
The last death came about due to a repeated use of phantasmal killer at 10th level used by a rejuvenating ghost who kept reappearing near to the bells he was bound to. He was raised, however, afterwards.
I also run a Midnight game where there's been one death, which occured at level 2. The characters were trying to sneak into a city, so as to avoid suspicion, were traveling in pairs. Unfortunately, a pair of orc guards caught onto this, and proceeded to lay into the pair of PC's that tried walking past them. Both were dropped into negatives and hauled in as prisoners. They didn't bother trying to stabilize them, so one bled to death on the way there.
I tend to be fairly forgiving in some circumstances, but don't want to take the edge off from the game.