Or reboot the machine. It works better when not only browser tabs accumulate, but also terminals, editors, virtual machines, etc. Just reboot it all to hell. It's a good chance to update and load a new kernel, anyways.

Also,

> Clean my desk completely.

It's amazing what having a clean environment does to productivity. After being more clean/neat in my life, I've found that clutter has kept a constant burden in my mind. Clutter just makes working/living less approachable. I mean this both digitally and physically.