I was just wondering...I know you can a dog..but is there any others

Usually it is me killing the companions, not the game. I learned that battles in 3rd person are better for companion survival.

I also make a save before I enter any dungeon and before entering a new cell in a dungeon after I make sure my companion is behind me.

Derkeethus is one I think.

Quest-giving guild members are essential, for sure.