*[Pocketknife][1]* is the most common term for this type of tool.  All Swiss Army knives are pocketknives:

![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:

![Multitool](http://dsc.discovery.com/survival/survival-tools/images/multi-tool-600.jpg)

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