The iconic StatTrak!" M4A4 | Howl is possibly the most expensive CS:GO skin and certainly the rarest. It's a contraband skin (the only one of this rarity), which means that you can't get it by opening cases anymore. In fact, the only way to obtain the Howl is through trading it with other players on skin marketplaces.

Will Playing On A Skin Changer Server Get You Banned? While Valve doesn't like skin changers, you will not get banned for simply playing on a skin changer server. These servers are usually called ws servers  and are not allowed by Valve in policy, but little is done against them in practice.