Yikes, there are so many out there, it's hard to make a choice. I never could figure out the thousands of multi-tools out there…I guess they're popular gift items.
Personally, I remain loyal to Swiss Army knives, because they're useful and not too heavy. The Swiss Army Climber ($35) is a great all around knife/tool. It also connects easily to a climbing harness to serve as a belay knife.
Thing is, knives don't have pliers, and pliers can be exceedingly useful. So if you want pliers you need something such as the new Leatherman Skeletool CX ($90). The Skeletool looks like something a Terminator cyborg would carry—Leatherman has re-thought the look and feel of a tool with this design. But it has all the stuff we have come to expect from multi-tools: blade, pliers, wire-cutters, Philips and flathead bits, bottle opener… The material is heavily drilled out to pare weight, and at five ounces it's fairly light. It also has the provision to be clipped to a short cord or something for access when climbing.
I also like the Gerber Suspension Multi-Pliers ($39), which add a small pair of scissors to the mix.
But really, just about every tool out there does the requisite things. My advice is to get into a store and heft a few. See what feels best in your hand. That's the one for you.