Depends where you live. A lot of this stuff can be acquired afterwards.
As an Aussie, firearms are very hard to come across. Also, I've never fired a gun before, so I would pick the shotgun because I know my terrible aim would be mitigated somewhat.
Water purifier. Duh.
Fire axe. Utility + weapon.
Tent. I live close to nature, so my game plan is to stock up on nonperishables and go camp for as long as I can, and hope that the zombies have thinned out by the time I need to start scavaging