Since the batteries are 12v and shore power is 115v, an inverter is required to scale up the 12v battery power to 115v to power "normal" household plug-in things, from power tools to computers. Whenever possible I will use the 12v system directly (i.e. car chargers), because it is more efficient than converting up to 115v then back down to, say, 5v for a USB phone charger or computer power supply.
Shopping for an inverter took a while, because there are a lot of of them out there. I decided that 2000w was enough for my purposes, though I wanted one bigger because I want more of everything. I wanted one that would also charge the batteries and "pass through" the shore power when plugged into an outlet.
I chose a ProMariner 02012 True Sine Wave inverter, largely because of the pass-through and charger features, and because it seems to have good reviews and reputation. I'm happy with it.