Are you talking about waterproof or weatherproof? The packs made out of Cordura 1000 are, for the most part, weatherproof. That's things like the Maxpedition packs, or Spec Ops. As I have mentioned elsewhere in these forums, I like to take a Star Trek approach...triple redundancy. Put the stuff that needs to keep dry in dry sacks, ziplocks, Lexan bottle...whatever works for you. If you're expecting a lot of water, you may want to get something with a drain hole in the bottom. FWIW, I just got a Max Pygmy Falcon II and started using it as a daypack. I really like it so far, although if you don't like the tactical look...
I got a khaki one, because I figured that was more neutral and less likely to draw attention (although one spry old woman wanted to know where I got it...thought it would be good for geocaching!). I wanted to get one in navy...even less conspicuous, but I got an awesome deal on the khaki one, so I had to get it.