I would definitely regret not taking many risks, like relationships, just going to certain hang outs, being emotionally available for others, getting my ideas into paper, getting my shit together and being motivated to do more productive things.
basically, everything that any rational person would regret if they were about to die. I don't know why death is what reminds us most about what we should be doing. Lol death is such a jerk that way.
I'd regret that I didn't tell more people that they are going through life like there is an ultimate goal, when in reality they will just rot in the the dirt. "Give up your earthly possessions! Nothing matters, and there is no heaven! Give up! Stop doing things! Sit at home and relish in the knowledge that life is useless!" Yeah, I'm going to go out and start my soap-box revival today.
A more serious answer from me: I am completely unfazed about going when it's my time. Will I wish that I could have done more? Probably. I can't say for sure that I wouldn't regret anything. I think that's just a part of the human condition and why so many of us fear death (aside from it being an unknown, obviously).
I'm already tired, I keep pushing on because there are people that need me and I love them enough to keep on pushing for them while holding out hope that I can help others and even our planet along the way. If I can make a difference that causes a small ripple effect I will be content with that. I don't need to be well-known, I have no desire to make sure I go down in history. As long as I make sure those that are close to me know that I love them and I pursue my hobbies... I will be regret free.
I can mull over it but I feel in my gut that when it is time for me to let go, I will and I will do it without regret or what ifs.
I will be elated to have some reprieve, finally.
Everything. The only thing important is being alive. So I'd be bummed at the fact that I don't get to be alive anymore. I don't want my life to end. Even if I don't "do anything" with it. Existence alone is fuckin' amazing.