Nah, but seeing as how Shuckle's biggest niche is its unique dual hazards, you're definitely going to want some sort of anti-Rapid Spin and/or anti-Defog support. That said, Bisharp and physical Thundurus are the main Defog deterrents in OU right now, and both very commonly carry Knock Off.I'd like to say that not everyone uses Bisharp, so if you're not using it, go ahead & Knock Off.