No-square sparer
Someone (Person A) who, when in a public restroom, refuses to give a person sitting in the adjacent stall (Person B) a square of toilet paper when Person B has run out of toilet paper. No-square sparers typically take high risks, as there is always a chance that Person B could exit the stall at the same time as them and initiate an argument.
Person B: Hey, person in the other stall, could I have a square of toilet paper?
Person A: No, sorry.
Person B: You don't have any?
Person A: I have some, I just don't want to give any to you.
Person B: Please? Just one?
Person A: No.

Person B: Don't be a no-square sparer...just give me one! How hard is it?
Person A: **flushes and unlocks the stall**
Person B: (overhears the flushing and stall unlocking) F**K YOU, MAN! I'LL REMEMBER THIS SH*T!