Multi-tools combine pliers or scissors with at least one knife blade and a few other useful tools such as screwdrivers -- and fold up compactly between uses. A full screwdriver or pair of pliers will always be easier to use, but a multi-tool give you a way to carry lots of functionality in a small package for quick everyday tasks.
Although it's tempting to look for a multi-tool with everything, reviewers warn about two drawbacks. The more tools inserted into a handle, the harder it can be to get out the one you really want. The second issue is that the more tools you load onto a multi-tool, the heavier it becomes. A multi-tool that weighs half a pound is fine for a glove compartment, but not much fun to carry around all of the time.
For carrying with you all the time, in pocket or on a keychain, Leatherman multi-tools get mostly positive reviews (Leatherman is certainly the best-known brand). We saw more positive feedback about the Leatherman Micra (*Est. $20) than about any other multi-tool. The tiny Micra includes scissors, tweezers, a nail file and a small blade -- plus three screwdrivers (including a tiny one for eyeglasses). The scissors are the main tool you get when you unfold the Leatherman Micra, and in general, Leatherman scissors earn high marks for sharp cutting.
Owners also like the fact that the tweezers on the Micra are built in, so they can't get lost. You do have to unfold the Micra to get to the knife blade or other tools. Then when you fold the handles again, you have a very smooth, secure handle. Larger Leatherman keychain multi-tools let you open the knife blade (and lock it into place) without unfolding the handles.
If miniature pliers are more important to you than scissors, the Leatherman Squirt PS4 (*Est. $25) unfolds to show pliers where the Micra has scissors. A tiny pair of scissors unfolds from the Squirt's handle, but there are no tweezers. For wiring repairs, the Squirt ES4 (*Est. $25) has more appropriate tools. At Amazon.com, about 85 percent of the owners say they're very satisfied with a Leatherman Squirt; complaints center on the scissors and some trouble getting the bottle opener out, though we also saw some reports that say that the scissors work very well.
These keychain multi-tools have one short knife blade, 1.6 inches long, and are light, less than 2 ounces total. The two Squirt multi-tools come in red, black and blue; the Micra adds green, gray and stainless steel for a total of six color choices. Like all Leatherman multi-tools, they carry a 25-year warranty.
If powerful scissors, a toothpick and a sheath are more important to you than a Phillips screwdriver, the SOG Crosscut CC51 (*Est. $15) keychain multi-tool provides all three. The scissors have compound leverage, and that has positives and negatives compared to the Micra. Owners comparing the two at the Multitool.org forum note that the Crosscut multi-tool makes short work of opening plastic clamshell packaging, but that paper can get hung up on the compound gears. Both tools are about the same weight and length, but reviews note that the Crosscut is thicker. Overall, feedback indicates that the Micra is a more useful all-around tool.
Stepping up in size, we also found some good comments for the Leatherman Skeletool (*Est. $45) and the Skeletool CX (*Est. $65), which has a carbon fiber handle. These multi-tools weigh about five ounces each, with knife blades that are about 2.6 inches. The main compromise compared to heavier multi-tools is in the strength of the pliers, which are thin to save weight. We found complaints about pliers breaking under very little stress. Still, reviews praise both Skeletool models for their nicely contoured, comfortable shape plus the easy access to all the tools -- no nail-breaking attempts to pull out a tool wedged into a handle. The knife opens one-handed, and the carabiner doubles as a bottle opener.
The main difference between the two Skeletool multi-tools is the stainless steel used for the knife blade. The Skeletool CX has a plain blade that's easier to sharpen than the partially serrated blade on the regular Skeletool. Also, the blade on the CX is made of 154CM stainless steel, which reports say holds an edge better than the 420HC steel used in the regular Skeletool.
The Skeletool multi-tools also have a universal bit holder in the end of one handle. This is a mixed blessing: it's easily accessible and you can use any standard bit -- but it's possible for a bit to fall out if the bit driver spring isn't just right. We found quite a few complaints about faulty bit holders, a nuisance even though such a defective tool would be replaced by Leatherman under warranty. Owners also report that the contoured handle makes using the screwdriver a bit awkward.
If utility and versatility are more important than portability, the Leatherman Charge TTi (*Est. $90) has four blades that are accessible without unfolding the pliers: a regular knife, serrated knife, saw and file. All the tools built into this model lock into place, and the total weight for 19 tools is 8.2 ounces -- heavy enough that the Charge TTi multi-tool is most appropriate for a glove compartment, tool box, desk drawer or tool belt. The Charge TTi comes with a removable belt clip as well as a sheath that has extra pockets to hold more screwdriver bits or a mini-flashlight.
Unlike the Skeletool discussed above, the Charge TTi folds the universal bit holder into the handle, so the bit can't fall out. The Charge TTi comes with eight driver bits, including a Torx bit, and you can also buy extra bits. The blade is 2.9 inches long and is made of S30V stainless steel.
The Swiss Tool Spirit (*Est. $85) might also be worth considering, and it earns kudos for tools that are easy to open -- all from the outside when folded -- and lock into place. The main negatives in user reviews surround the knife -- it takes two hands to open and is mostly serrated, with a blunt end like a butter knife. Also, some reviewers lament the lack of ruler. A kit of extra driver bits is available, but they mount on a completely separate little tool, not the Spirit multi-tool itself.
We found the comparison review of multi-tools at Popular Mechanics helpful because it covers three major brands, even though tests here cover only five of the many multi-tools on the market. The nonprofit Multi-Tool Museum site also provides a good comparison review, and we also found some useful comparisons at Crunchgear.com, HandymanClub.com, and MultitoolGuide.com. We found expert single-product tests at Wired, Backpacker and Outside magazine magazines. Amazon.com publishes the most owner-written reviews of multi-tools, but reviews at REI.com, Backcountry.com, KnifeCenter.com and Walmart.com are also helpful. YouTube.com provides loads of video demonstrations and reviews of multi-tools -- helpful once you've narrowed your choice to two or three models.