The Multi-tool has eliminated us from having to carry a plethora of bulky equipment. It can also replace a tactical folder that would normally be carried in your EDC kit. Again eliminating things that need to be carried.
Multi-tools have saved me plenty of times and helped make bad situations a little better. I rarely carry tools in my vehicle (I know, a sin) other than jack and tire iron. I've made small repairs while on road trips and have cleaned fish when I left my fillet knife at home.
Most Multi-tools feature a small folding knife that can compliment your B.O.B. fixed blade. Able to do finer task work like skinning game or fish. Most have a saw that can help you gather kindling or when making trigger traps. I use the file as a ferro rod striker and it works very well. The other tools are pretty self-explanatory and provide you with a variety of functions (especially when surviving in an Urban area).
My first Multi-tool was a slide out type made by Gerber. I used it for about six months when it decided to go poop on me. I'm not sure if I may have had a bad one or their quality assurance department was on vacation the day mine was put together. Either way, I've since gone with Leatherman products and have yet to have them fail me. With that being said, I recommend Leatherman tools over the rest. Since we are looking at cost effective options; we will stay with the lower priced offerings from Leatherman.
The Leatherman Blast pictured above is a tough tool that has enough features to handle most task. It's uncomplicated with less room for failure. This is the tool I keep tucked away in my B.O.B. I keep this in the B.O.B. since I use my more expensive models on a regular basis in my EDC bag. I can't see having a $100 Multi-tool collecting dust in my go-bag.
The Blast comes with: Pliers, Wire cutters, Knife, Saw, File, Lanyard Ring, Phillips/Flat head screwdriver, Small glasses size Flat/Phillips screwdriver, Scissors, Bottle/Can Opener (no need for a P38), and Ruler. This tool can be found on Amazon for around $33, I've also attached a link to the Sidekick that retails about the same. Regardless of what model you choose, make sure you have one in your B.O.B.
By all means if you find something better that works for you go with it.