I always take a multi-tool.  It keeps me from taking several other tools (pliers, knife, file, etc).

I use it all the time, and there have been times when I have had an equipment failure and really needed a screwdriver.  I use it all the time when fishing to cut line or take out hooks...It is a tool I don't leave home without.

It is one of those things that you don't really know if you need it, until you need it, then you are really glad you had it.