What are some really rare unique mental diseases or disorders?

Serious answers please....
What are some rare but interesting disorders? Please give a little brief description of them if possible.........

Capgras' syndrome is the delusion that a loved one has been abducted and replaced by an exact duplicate, by (chose one) CIA, Russians, aliens, neighbors.

For other mental oddities, you might want to read something by Oliver Sacks.

Ummm.......you're a freak.

I suppose this is rare....it's called body dismorphic disorder.......where the person contantly thinks they're ugly

lunarcy. its the old form of werewolves, not diagnosed lately coz its politically incorrect.

Agoraphobia = people who cant go outside, they are stuck in theyre houses...weird!

These days I think sanity is the only mental "disorder" everyone doesn't have.

Munchhausen by Proxy Syndrome is when a mother or father harms their own child in order to obtain attention/ sympathy for themselves. (Like the little girl in the Sixth Sense who's mother feeds her soup with Lysol in it.)

schizoaffective disorder affects only 1% of the earths population. is that rare enough.

look at website below