What would be the lowest cost and most fuel efficient vehicle for a post 2012 Apocalyspe world?

the date fixed by you is quite near.
select some other year. nothing is going to happen in 2012.
the technology has not advanced so much which we may tell beforehand?

A blow up raft

Just have rays and cockroaches carry you around

Your feet.

But, not to worry - the world isn't going to end anytime soon. And if it does, you won't even realize it.

a bicycle