Old people. I don't know why, but older people have that distinctive smell. It's not overly terrible, unless they're having bowel control problems, but it's not the loveliest smell ever. Using the same old lump of soap for your weekly bath, deciding that you're that old, it no matters how much care you put into brushing your teeth, sitting around 24/7... Sometimes it is comforting though, if you have an older relative that you've bonded with.

Also, I'm probably the only fool has done this, but anyone ever left your swimming bag in a corner somewhere, and forgot to get your swimming gear cleaned? It was a strong smell of damp and chlorine when I found my bag a week after I'd been swimming. ><

OH. Old milk. ****ing seriously. It smells like baby vomit (which is gross anyway). I do the recycling as one of my chores here, and I once made the mistake of opening an old milk bottle to flatten it; instead, I just pushed the stale, disgusting air out of it and into my nose, and I almost puked all over the kitchen. I'll never make that mistake again.