Ten points for/from Gryffindor

In the universe of the Harry Potter series, Hogwarts is divided into four houses, each bearing the last name of its founder: Godric Gryffindor, Salazar Slytherin, Rowena Ravenclaw and Helga Hufflepuff. The houses compete throughout the school year, by earning and losing points for various events, for the House Cup (correctly answering a question in class, for example, may earn five or ten points; lateness to class may cost ten points).

This expression is commonly used between video game players and *chan users to compliment/mock someone on an achievement/fail. The expression itself has evolved from just being a Harry Potter reference and is now a common way of stating that something is lulzworthy or not.