Swiss Army Locksmith knife is pretty handy to have. Its certainly not the toughest but it has a remarkably effective main blade for its size. It is cheap at around $20 and has lots of other useful features such as a good little saw blade, tin opener, awl, screwdrivers etc (using these tools means you don't have to abuse the main blade for difficult jobs). Folks around me also tend not to get to excited when you pull a SAK out from your pocket. The SAK is also easy to sharpen.

http://www.amazon.com/gp/product/B000687...;pf_rd_i=507846

Where as my Kershaw mini cyclone ZDP-189 may make them slightly more excitable.

http://uk.youtube.com/watch?v=kaNUP5ATp9o