My favorite multitool is a Leatherman Pulse. It has a good complement of useful tools (but not too many of them) and they all lock very solidly. It's also reasonably sized and not too heavy. If it had a saw in place of the knife blade, it would pretty much be The Perfect Multitool.
I also have a Vic Spirit, and it's good. I like having all of the tools easily accessible on the outside of the handles, but the tools themselves are a bit strange. Leatherman's tools are easily identifiable with just a glance, but with the Spirit I always have to look and turn it over a couple of times. Some of the Spirit's tools are also kind of stubby, e.g. the small screwdriver of top of the can opener is almost useless. But it is ergonomic and very, very well made. The knife blade is really nice, too.
I had a Leatherman Wave (the new model), but I found it a bit too bulky and heavy to lug around, so I sold it.
I just won a SpydeRench on an internet auction today, but I haven't seen one before, so I can't really say anything about it yet.