I have a Snugpak Sleeka and really like the size and weight of the pack. Good price too.
I keep a little backpacking stove, couple of fuel canisters, cup for heating water/coffee/tea, etc, along with a collapsible drinking cup, Nalgene bottle and a couple of other bottles of water. Also have a compressed down jacket, and Goretex shell, spare socks, gloves wool watch cap, etc, along with a small 5'x7' tarp for making a shelter, or just as a wind break. I have 550 cord.attached, so it sets up quick. The small tarp is a great piece of kit, and makes a world of difference on snowy/rainy days.
I also keep a small Husqvarna cruisers axe attached on the side.
In Ziplock bags I have makings for tea, coffee, sweeteners, etc, as well as a couple of "Mountain House types meals and other foods that are not temperature sensitive. Basically a couple days worth of food. There are also a couple of redundant ways to make fire. Plus a headlamp, and small LED flashlight that takes a single AA battery. There are a few more things in the pack, but I think you get the gist of the size, capacity.
On the top of the pack is a separate pocket that fits a holstered 1911 and a couple spare mags.