Very interesting thread - thanks for starting this one.
I'm in my late 40's, never married, no kids, and no plans for either. Although that could always change, I'm pretty set in my ways and love my freedom and independence, so it's doubtful I'll ever have to worry about leaving something to a partner or kids.
My parents are both gone, so no eldercare needs.
I have three siblings, but I didn't grow up with them because I'm much younger than they are. Because of the age difference, two of them have already retired, and the third is retiring soon. It might sound harsh, but I wouldn't leave money to anybody (even my own siblings) at the tail end of their careers because I figure they had their chance to feather their own nest for retirement, and I'm not feathering it for them. I also don't want, nor expect, to be a beneficiary in their wills.
So that really only leaves nieces, nephews, and their families, but the problem is, I don't really know them. Because of the age difference between me and my siblings, we didn't grow up together. They were already moving out of the house by the time I came along, and my family was never the kind that got together a lot for family events.
I see my nieces and nephews maybe once every 7 or 8 years. Other than that, I never have any communication with them. So I doubt I'd leave anything more than a small token amount with them. I certainly wouldn't leave tens or hundreds of thousands of dollars.
So my plan is to spend it on myself and enjoy it. After 30+ years in the rat race in a career I've grown to hate, I want to bail and spend my remaining time and money on traveling, and doing things I've wanted to do for a long time.
If there's anything left when I croak, I'll leave it to my church, who is already named as the only beneficiary on life insurance policies and my stock option grants at work.