Parry this you filthy casual!

Parry is a mechanic in games which is usually blocking an attack right before hitting you, the phrase "parry this you filthy casual" is commonly used in memes to refer to attacks and enemies known to be hard to parry and defend.

Can be used in real life when attacking someone out of nowhere

*at dodgeball

See that dude?, he hasn't been hit until now and he isn't looking.
PARRY THIS YOU FILTHY CASUAL!