Borderline Harassment

Enchant player
Whenever enchanted player spends mana, any
opponent may ask him or her to pay x additional
mana, where x is half the mana he or she had
spent rounded up. If enchanted player does, the
player who asked discards a card. If enchanted
player doesn't, the player who asked draws a card.
Multiple players may ask on the same trigger
and must be paid seperately.
by PBRunny