Would Ты prank your friend with their greatest fear?

No, I'm not that cruel.

Their greatest fear is being pranked, so I will win like a boss.

My friend is scared of urine.

...

Does that mean I piss on him? I hope not o A o

No i wouldn't. I'd prank them with 'partly' their greatest fear, but as soon as i know they're ready to quit i would quit.
Never prank anyone with their greatest fear unless you're ready to be revenged upon by your greatest fear.
I would hate to think of my Друзья would prank me by using spiders, или confining me in a coffin under the ground или somehow making me think i Остаться в живых a lot of blood.

Of course.

Story time:
Last year, my friend brought a plastic паук to school. We tried scaring people by throwing it in their faces and stuff, but they weren't afraid of it. We did it to gifted grade 7s and they told us their friend had a fear of spiders. So we gave them the plastic паук and she went and put it on her shoulder. Then she told the girl there was a паук there and she started screaming then crying. Then the колокол, колокольчик, белл rang, my friend collected the spider, and we went to class. At least we got rid of the girl (she was really annoying and after that, she never spoke to us again).

No, but if they will prank me I'll prank them too

My friend is afraid of death...so...I wouldn't wanna kill her.
Maybe I could dress up as the Grim Reaper или something :S

With their greatest fear? No, this would be dangerous and might drop a bomb in my life. But with the greatest fear, honestly, I would.. I'm a professional trickster. ^_^;