The only problem I have with bringing tools into any fight is that anything you have can be taken off you and used against you in a fight. Of course, if the other guy is armed first then that negates the point, but even a set of keys can make for a pretty good slashing weapon in the right hands. Used to be a popular tactic for the 'Firms' back in the day. This site shows a few good examples, although their 'phone' is somewhat more of a brick than most phones of today:
http://www.urbancombatives.com/weapons.htm