I sleep in underwear with a night gown over it

I sleep in a nightie most nights so I guess t shirt would be my vote, if it's really hot though I do tend to strip off.

Nude. Not sure why you would need to put on any clothes - they don't serve any use, and whoever ends up in your bedroom is someone who's probably seen you naked already anyway.

Of course, when I'm sleeping over at friends, I usually just take off my pants and socks, so I end up sleeping in shirt + underpants.

Nude for me, im the same i cant stand clothing on me as i move about, if i wear something i wake up in the night and throw it off like and go back to

Simple pajamas, where I live is hot so I use light ones

i have slept nude or in a snug t-shirt my entire life.
i detest clothing on myself while i am sleeping because it gets twisted up (specially bottoms) as i move through the night, so no thanks