Granted. You recieve several circular slabs of ammonium diuranate, also known as yellowcake.
I wish for a large comet to appear near Earth tomorrow.
Granted. "Congratulations! It's an... alien?"
I wish for a [REDACTED] sign.
You receive your sign in the mail, it was everything you could have ever wanted in life and you become crazily obsessed with interacting with it physically that you grow socially inappropriate by locking yourself in small confined spaces with the sign and whispering questionable things. Your insanity continues for years as you become miserable with no other desires in your life that you commit suicide using a blunt edge of the sign.
(better love story than twilight)
I wish eyes got smelly instead of feet.
Granted. Your eyes rapidly become extremely smelly due to strange secretions of hydrogen sulfide. Your feet, instead of becoming smelly, secrete sulfuric acid. This does not occur to anyone else, leading to your imprisonment in a teflon-lined cell in a lab somwhere due to your corrosive and smelly nature.
I wish that mercury was not a toxic element, along with its compounds.