Loo, Restroom, Bathroom, Water Closet or WC, Ladies Room or Men's Room (depending on your gender), Little Boy's Room or Little Girl's Room, crapper, head, latrine.
You can also say:
"going to powder my nose,"
Here are some slang terms for potatoes:SpudsTatersMurphyTots
There is no part of a toilet that's called a 'slang'
Some slang terms for arsonist are firebug, torch, and pyro.
fine
The slang terms I'm familiar with are: P.I. Private Eye, Peeper and Dick
Here are some examples:CarJalopyFlivverRide
bucksgreenbacks bills
Pito grandote
shela
Angel dust
Hoops, bangs
soda is sody