*[Pocketknife][1]* is the most common term for this type of tool:

![Pocketknife](http://photo-dict.faqs.org/photofiles/list/821/1248pocket_knife.jpg)

But *multi-tool* would work, too, especially if the tool in question is not a pocketknife.

  [1]: http://dictionary.reference.com/browse/pocketknife