Consider the manual for fighting zombies by Max Brooks- with many of us living in populated areas, it would be easy for us to obtain the weapons we need.
I would abide by the "three-ranges" ideal, with the attempt at combining tools as much as possible to lower total weight. My primary would be something like a Semi-automatic rifle (with an added low-light scope for night attacks) which would force me to conserve ammunition all the while giving me much needed range. Most semi-auto rifles use easily obtainable ammo (I think 7.62 mm Hungarian Heavy Ball) and their single-shot methods make them easy to repair and clean.
My secondary would probably be a .22 rimfire pistol. Small enough to be easily concealed, yet powerful enough to punch through a skull, the diminutive .22 is an easily underestimated gun that can come in handy, even in close engagements. Since it's ammo is also so light and plentiful, I doubt a gun shop wouldn't carry less than several thousand rounds. Their size (1/3rd that of most other rounds) means that transportation would be a breeze.
My final weapon, for close-encounters or hand-to-hand, would be the ever-prevalent crowbar. While obviously a useful tool against the undead,it serves the secondary function as a lever for wrenching open things like doors, giving it a good level of utility. If possible, however, I would get the newer Titanium models that have been leaking into the US from the former Soviet Union and it's once-European Allies, since they weight less and are much stronger than normal steel.
Course, that's just for standard, smaller engagements, and nowhere near what I would use in a building...