Quote Originally Posted by LvivBoy View Post
Actually you can't call someone косяк. This doesn't sound right to me at all. You can say "он косячит" instead.
Yes, you can! As well as косячник.

Just a few examples over internet

Витя Ну ты и косяк!1 Да еще и конкретный ахаах XD, Мем твое выражение лица -
https://vk.com/kosyaktw