Death by suffocation seems to be my big trend. My last two most aggravating deaths:
No Lanius crew, but a particularly intense battle saw my O2 down, doors destroyed, clone bay damaged in a battle amongst solar flares. I did an emergency jump out straight into another battle against a pirate who was getting absurdly lucky with fire weapons. As a consequence, it wasn't until half my ship was in vacuum that I realized that despite a now-working life support system my crew was slowly dying. Eventually I found the cause; the tile containing the cloning tank was breached. It was almost completely obscured by the cloning tank's sprite, and since the clone bay was only two tiles large I could only get a single dude in there to try and work on it. Turned out to be academic, as the fires brought my shields down and the enemy halberd beam quickly sliced me up.
My very last run was with the Mantis B. I had a full boarding party of 4 murderous bugs along with a support crew to man the ship, but only a couple of anti-ship weapons (one of which ran off of missiles which I had very few of). While fighting an auto-assault, I jumped two of my boarders over to destroy the other ship's shield generator so my conventional weapons could finish it off. I had an upgraded teleporter, which would allow me to snatch my bugs away just before they died of suffocation...at least in theory. What actually happened was that the auto-assault cloaked just a few frames before my teleporter's cooldown could finish, thus dooming half of my boarding party. I tried to continue on, only for a random event in the very next jump to kill a third mantis. Because I was heading towards the endgame and now lacked any way to win short of ludicrous evadehax on my part, I quit.
FTL: Faster Than Light.