This is one of those topics that always seems to be active somewhere on the forums.
My current favorite multi-tool is the Gerber Legend (aka Multi-Plier 800). It offers a fairly common set of functions, but several of them are unusually capable.
The pliers spring-open and have comfortable handles. The wire cutter uses replaceable tungsten/cobalt cutters. The saw is actually a mechanism that can hold any standard 2" jigsaw blade; it comes with one for cutting metal.
All tools are accessible with the pliers closed. All of them lock, but are easy to unlock.
Both the knife blade and the scissors are equipped with thumb-studs which allow them to be opened with one hand. The unlocking mechanism also allows them to be closed with one hand.
Finally, the Legend is built for heavy use, but made of lightweight materials. It isn't too big or too heavy to carry with you all the time.
Over the years I have carried the original Leatherman, the BuckTool, the Leatherman SuperTool, the SOG PowerPlier, and the Victorinox SwissTool. The only one I was ever unhappy with was the Buck, but I prefer the Gerber Legend to all of them.
--Bob Q