Use a [toilet plunger][1]. That's what it was designed for, and if you use it right, won't splash at all. Most people have one by te toilet, or in a small closet nearby. It's far more effective than using a brush, and much less messy.

![enter image description here][2]


  [1]: http://en.wikipedia.org/wiki/Plunger
  [2]: https://i.sstatic.net/lovAL.jpg