less a genuine idea and more a fleeting daydream-like thought i've had, but i always thought about having a caretaker or loved one take my life themselves (through sheer brute force, or a firearm, or similar.) i had my life threatened multiple times as a kid, so i guess that sort of just warped into obsessively thinking about how to provoke the other person just enough for them to follow through with those threats. see also: getting kidnapped and having the kidnapper take my life.
i guess if it were up to me, and everything went as it did in my head, i would not be the one responsible for making sure i CTB.