It smells like paint if you're really old like me. ;-) The kind of paint I'm talking about is based on linseed, or flax oil. It's nothing like modern petroleum based house paints, or of course, latex paints. But this is a really strong smell. The comment above about art-supply smell is correct, as most artists oils are linseed oil based.

If you have an old popcorn popper around (not an air popper), just open it up and smell it. Most people just wipe them clean, leaving a nice layer of oxidized oil on the surface. If you have a used deep fry daddy/baby around, smell the plastic lid. It's likely tacky with rancid oil. These too are strongly rancid smells. You're unlikely to encounter something this rancid in a bottle.

If anyone in your house is a ramen eater, just look through the packages, and pick the one that shows canola or cottonseed oil as part of the wheat noodles (they're usually deep fried in it) and smell the noodles. They're covered in rancid oil. The older they are, the stronger the smell, of course.

All the brown rice I've encountered recent memory has smelled rancid, too. So if you have a bag of that hanging around that's been open awhile, smell it as an example. It's most likely rancid. It's a far more subtle smell than the above items,but it's there.