Here's a slightly more modest and realistic arrangement. You know, no RPGs, bazookas, infinite ammo, AK47s, tons of grenades or any of that stuff. You have to keep in mind you're in a zombie apocalypse and you probably won't find half of these things. However if given the chance I would obviously stock up on these things (and more).
First off, I would always have a good knife and a pistol with me in case I run out of ammo or I get too close to zombies. It is essential to have some sort of a weapon to fallback to, for whatever reason.
As for the main gun I'd go with, it depends on the situation. If I'm working alone, I would carry both a machette and some sort of an SMG (silenced, preferably). If there was no reason to be alarmed, I would kill everything with the machette or the knife within close range. Otherwise I would use the SMG, but really only if I truly needed it. SMGs are flexible in terms of carrying, they have decent ammo and fire pretty quickly. Great for getting out of a mess.
If I was working within a group, I would pretty much use the same equipment, but would distribute the tasks evenly. Everyone would have a knife and a pistol to use in emergencies, as I've said above. Half of the group would have machettes or axes to eliminate the smaller crowds without alerting other zombies. The other half would have some kind of SMG or assault rifle (all silenced, if possible), but would not fire them unless absolutely necessary. Until then, they should carry their knives and help clean out the zombies that are walking towards the group. No one should waste time with zombies that do not represent a threat to the group.
If things go south, the guys with the SMGs would take control of the situation and everyone else should pick up their pistols and try to escape in as little time as possible. If necessary, I would even have a sniper or two in a tower or something to provide a little backup. This depends on what the plan is though. If the group is moving out, then clearly the snipers can't stay behind.