The last user icon in the /people/ list vibrates... it seems to scale vertically one pixel up and down really fast. One of the more bizarre bugs I've encountered :)
There's no way to sort the /people/ list so I'm not sure if it's always the last icon. My colleague reported that the 'Edit members' screen of a project has a vibrating icon for another user, which is not the last in the list.
Also, I don't know of any good Windows software to record the problem?
User agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0
Platform: Windows 2012 server x64