Just remembered: got three dogs killed as well. I never use them now because they are so annoying. And I don't usually bother with followers when using stealth.

2. Lydia and Feandel, The wood elf from Riverwood.
Lydia died in battle against a Necromancer, and I sacrificed Feandel for Boethia's quest

So far, none.

To tell you the truth, I am terrified. I'd love to bring J'zargo or Kharjo out with Ra'vhash as he goes about on his merry adventures in Skyrim, but I just don't want to lose any of them to some foul play.
(Currently playing the Xbox 360 until I get Skyrim on the PC later on in the year.)

But I guess I'll just have to svck it up. There can be no gain without a little sacrifice, eh?

ive actually killed my companions myself with careless shouts (2 puppies and the whiterun housecarl)

Mjoll cannot die, she is essential.

The Khajit that guards the Khajit caravans. You have to do a quest for him before he becomes your follower, I cant remember his name. I went through so much trouble to make him my follower just so he could be sacrificed to a certain Daedric Prince.

None. Derkeethus can't die under normal conditions.

Lydia died twice whilst following me. I have kinda got lo like having her around even though she can be annoying. So I load a previously saved game.

1, anneke crag-jumper. I didn't like her name, and discovered I needed to sacrifice someone. forgot to take her gear first. I will miss you legendary dragonscale armor! oh... and you too anneke... I guess. You look better as a daedra anyhow.

I have never ever got companion killed by someone, I kill them myself.

Onmund died a horrible death after he got himself impaled on some bandit's sword and Lydia got torn to pieces in the battle against ... erm... I gues that's a spoiler. The battle against the very last person in the Mages guild quest!

Just the two I have needed for quests, I fly solo.

I think I'm up to 6, with my new character I'm not using companions though, so sad when they die cause they won't run from fights like I do. T_T My first character lost Lydia by accidently walking near the giant area NW of Whiterun, didn't know the mammoth symbol meant giants at the time, felt so bad. lol

Sven was my first follower. Didn't completely understand how they worked then. Got him killed by "bandits".

After Sven died, I got Uthgerd. She died in my first non-story related dragon battle.

Now I'm on to J'zargo, and I just reload the save if he ever dies. On the upside, he has one of the better AI's for a mage/shadowspell and can generally keep himself alive.

In my most recent campaign Lydia died purely by accident. I;m playing as a Dark Elf Assassin, with Daedric Quests and the Dark Brotherhood in mind. We were in Redoran's Retreat. I had chosen to practice my sneak skills by raising the fallen bandits from the dead, creeping behind them and stealth killing them.

Unfortunately Lydia and my Bandit Thrall were standing a bit close to each other, and shoddy targeting resulted in her untimely death by slitted throat.

She never saw it coming. But at the same time, ironically, neither did I !

Only one, and that was Belrand when he had an "unfortunate accident" at the Shrine of Boethiah.

Jenassa died on our way to High Hrothgar, smashed by a frost troll. I was too weak to defeat the beast and yelled at her to run, but she fought bravely to give me time to escape. I thought she'd follow, but alas, she didn't make it.

Just minutes ago I had to kill Iona. I came home with my newly acquired follower, Ogol, and the second she saw him she started attacking him furiously. Not knowing what exactly was going on, I had to protect my friend and shot an arrow straight into my housecarl's brain. I'm still not sure what came over her, but I found mead bottles on the floor, so perhaps in her drunken state she somehow perceived the Orc warrior as a terrible threat. Oh well. I didn't like her anyway, she scared me out of my wits when I first came into Honeyside and saw her sitting there in the dark, munching bread. She was creepy. However, she apparently liked me, because she left me inheritance of 300 gold.