I personally don't like separate tools because they rattle around, of course you can always wrap rubber bands around them. I carry the Park MTB3 multi tool plus a small Leatherman that has folding pliers in it, along with tire irons and a QuikStik. The MTB3 has tire levers built into it but they won't work on a road bike because their too wide but work great on MTB tires, thus if you have a MTB you won't need to carry separate tire irons.

There are at least 2 dozen kinds of multi tools on the market, I recommend you go to your LBS and look at the selection and see which ones have the tools you need more of. Then get a folding set of pliers because no bike specific multi tool comes with one...why not?