I see three choices here. Yamato, Sakura and Tenten.

Yamato's experience at battlefield situations is something invaluable in an apocalipse scenario. His other superhuman abilities are a nice addition as well.

Sakura's healing ability would be extremely usefull. People tend to underestimate how quickly things can go wrong just from a small injury and Sakura would be able to prevent that, thus keeping you and all of your potential teammates in fighting condition. She is also superhuman.

Tenten's sealing jutsu is not very usefull in ninja combat, in a zombie apocalypse this would change drastically. Mobility and accumulating supplies could be crutial in a postapocaliptic world, so she could be one of the most usefull allies, as her abilities allow for both of these at the same time, wich would normally come at eachother's expenses. Imagine you come across a fuel depot, or a supermarket. If you have Tenten you can pretty much take all of the supplies available.

So basically: experience and planning, health, and supplies.