Additives: what works what doesn't?

[Rooster's82]

I was at the auto parts store the other day and I started looking at all the oil additives and transmission additives and so on and so forth. Some of the claims are ridiculous but others seem like they might actually help.

I know that I have not narrowed it down much too any specific additive I wanted an opinion on, but really what I would like to know is what everyone uses and what you wouldn't pour in your worse enemies engine/transmission/gas tank/radiator...

a couple examples, super lubricants, engine seal conditioner, transmission restore, engine cleaner (the stuff you pour in your oil and run right before an oil change), engine restore....