I wouldn't say attemps, more like "simulations" and "experiments" to say how it would work. I've pointed a gun at my head but I wasn't planning to ctb that day, plus I didn't want to make the owner feel guilty, also if you are going to use a gun, nobody should be in the house trying to rescue you, to increase your chances of dying. So there's that, I didn't do anything with the gun.
I did an experiement (several times) with some materials, several tries with the wire of my headphones and with shoelaces for partial hanging. I managed to get dizzy, but that's it, and it was a very specific spot, couldn't risk it. You need a thicker rope that can sustain your weight. I was caught once doing this and it was extremely embarrassing btw.
I made some trials with razor blades on my thigh, to see how easy/hard it would be to actually cut my carotid arteries on the neck. Welp, the statistics are true, it is very hard. There is a lot of pain, and even if you ignore it, there's no garantee that you will hit the right places. Cutting is one of the hardest and least successful methods. Forget about it.
So I have never seriously "attempted", but you could say I'm no stranger to self-harm.
My next method is SWB, which requires training, lots of training.