Black Sakkat 'Sins

From Euphro

The term "black sakkat sin" is used as a collective term for assassins preferring a certain palette (black) and headgear (sakkat). They have also been known to wear Sunglasses and a Flu Mask. These people are usually looked down upon as unoriginal and "newb"ish.

Lumped under the same category, regardless of whether or not they're wearing Sakkats or black clothes, are the generally bad Assassins who will only target first class characters in PvP, and attack with a single combination of skills - Sonic Blow and Cloaking.