I have the same icon, but it's for my printer since I use it through a USB port. The icon only appears from some devices, that need to be stopped, before unplugging. It would probably appear for those, who use a USB hard drive or such. Doesn't show up for my mice though.
I got it as well for my USB cable modem, what I do is go to the taskbar properties, then customise hidden icons. just set it to always hide. You'll get the arrow to expand the icons in the system tray but it means you dont have to look at it all the time.