Yeah, giving colleagues concussions sadly is not an option. But if the bullying is taking place in the workplace, there are other options - although it does still come down to making yourself more of a hassle to ignore than to listen to. HR exist to protect the company, so making the point that the company has to provide a safe and harassment-free environment for employees, and therefore have to deal with bullies, can be a good strategy - basically implying that failing to deal with the bullies can get them sued. And depending on what country you're in (ie, whether you have good worker protections), if you've reported bullying, they haven't done anything, and you're left with no option but to quit in order to escape the bullying... the employment tribunals will be brutal for the company.