New Zealand! Two Islands, one is sparsely populated. Mountainous terrain and plenty of large rivers - perfect natural barriers. Loads of hunting rifles and what not floating around. Army is armed with NZLAVs http://en.wikipedia.org/wiki/NZLAV (Similar to US Piranhas), armed with a 25mm Bushmaster.
Some naturally produced gas. Plenty of fresh water, livestock and fish. Coal is plentiful for heating. Seasons are mild. Total population of 4 million. Huge hoardes aren't going to form as they will in more densely populated areas. For example, assuming that 100% of the population reanimate:
New York - 8.36 Million People in 1214 square kms (1 Zombie every 145m, an area 12m x 12m)
United States - 307 Million People in 9,826,630 square kms (1 Zombie every 32,008m2) <- This includes Alaska.
Japan - 128 Million People in 377,873 square kms (1 zombie every 2952m2)
New Zealand - 4.3 Million People in 268,680 square kms (1 Zombie every 62,483m2)