Yu-Gi-Oh slang for a player (often of high ranking) who is constantly and obsessively bitching over rulings. When ever a rule shark comes across anyone who breaks the rules is even the slightest way, even mistakenly , they will do everything in their power to get the person penalized. Rule sharks are most often found on the now popular Dueling Network website where they prey on unsuspecting victims in rated matches in order to gain rank. Most rule sharks go un-penalized due to the fact that they are technically not breaking the rules, however if one is proven guilty of rule sharking it is treated the same as boosting ; a form of cheating. Rule sharks are the reason most players avoid competitive matches
Player 1 mistakenly uses a card and takes his move back.
Rule shark: Hey you cheater you cant do that
Player 1: Sory, I messed give me a sec
Rule Shark : Why? so you can cheat more
*Rule Shark calls admin*
Player 1: Dude, what the hell.
Admin: Ok, whats up?
Rule shark: He's Cheating and he cursed
Player 1: But I....
*player 1 has been baned*