The best adjustable wrench known to me is made by Facom (makes tools for Ferrari F1). I have a few of them and the thumb screw has ZERO slop and locks up instantly. They have tapered ends so they can fit into more places, and they are precision ground so the two adjustable "ends" are exactly parallel.

http://www.toolstop.co.uk/facom-113-...wrench-8-p4158

I paid $30 for my 6" which is not too bad. My Craftsman Professional combination wrench set was about $80, so you make the call.