I think having cash is important, but I would rather have barter-able goods such as canned food, bottled water, ammo, alcohol, medical supplies, and high demand everyday common items such as TP.
He who has excess TP will become a VIP in the coming apocalypse. :-)
I've got a year's worth of TP stocked. Unless a girl moves in; then maybe 2 weeks worth.
If you live out in the country like me, a real good investment is a deep water water well with backup generator. Talk about a bartering chip come SHTF time.