Loaded question alert: (BEST MULTI TOOL)
Everyone has the best idea of what it should be.
Below are MY OPINIONS!
Here are the best in MY opinion (In MY order):
1. SOG PowerLock (one handed pliers - easily flip open, completely customizable)
My review and others (and links to others Like Frank K's comparison to the LM supertool and ) here:
http://www.bladeforums.com/forums/showthread.php?t=161220
Manufacturers website:
http://www.sogknives.com/pwrlck.htm
2. Leatherman Charge XTi (Ti):
There are many reviews and opinions in this forum.
I checked one out in the store. I like all the features, but THE BITS ARE VERY SHORT. If you need to get into tight spaces with a driver, you may be in trouble. The 154CM blade is worlds better steel than we are used to on a multi tool and makes this the current leader here.
One hand blade is of course nice to have.
http://www.leatherman.com/products/tools/default.asp
The extra bits fit in the sheath (which is LOW quality but passable).
If it had longer bits/drivers I would use this over the SOG.
#1 and #2 cannot be beat IMHO. If you need lots of different drivers, the Charge comes with quite a few and even more are available. I like the compound leverage on the SOG pliers and I have changed and modified many of the SOG tools -- SOG tools are hex bolt construction, you can take them apart to clean/fix/change out tools. They both have all components locking.
3. SwissTool - There are different versions of this and I have heard that they are heavy and built like a tank. Same amazing quality as swiss army knives. Many here call this their favorite. IMHO, it falls behind the top two due to the lack of one hand blade or pliers operation. Excellent choice if that is not required.
These are definitely the top three. The LM Supertool used to be up there but I think the charge has surpassed it, and the BLAST is looking to replace it (see below).
5. Gerber 800 series LEGEND:
Some like this one. I do not particularly. Do a search for it here.
4. Leatherman BLAST - Here we see a basic leatherman with all the tools of the old wave, but in an internal format. If you can live without a one hand blade (old wave, new wave, Charges), this is the best deal for the money. The pliers are identical to the new wave and charge, but with zytel handle inserts where your hand presure is applied. Longer drivers (permanent) than the interchangable bits in the charge/wave. Locks are the same as on the Wave/Charge and much better than the Supertool.
Permanent tools and no need for specific sheath to hold bits. (good for someone who loses stuff?

)
Small/MED tools
5. LM juice line. For non-heavy use or an office environment, these are perfect. All of them are slipjoints (no locking components) and will easily replace a SAK or similar item, but with the benefit of a med/small LM style pliers.
6. Swisstool Spirit. Some here have these, I have not seen one yet.
7. SOG powerpliers.- same quality and compound leverage as the SOG powerlock, but non-locking components.
Keychain size (might be nice to have in addition to the above - tweezers and an extra driver can be useful):
1. LM squirt: P4 (pliers) or S4 (scissors). Well made, tools access from outside. Upgrade to the LM micra line.
2. SOG crosscut(scissors)/crossgrip(pliers): Same SOG compound leverage.
3. LM Squirt radio shack (only) edition: mix of P4 and S4 features with the addition of wire strippers in the pliers head.
This is off the top of my head, so If I missed something, feel free to comment.
Since you are doing rescue work, it seems that the one handed blade may be the most important feature. The LM charge seems like the best option. However, if you carry a one hand folder anyway (like a spyderco resucue for instance
http://www.spyderco.com/catalog/details.php?product=72 ) you could consider others.
P.S. I carry the Powerlock and a one hand folder, so I have one hand pliers and one hand knife.