What gauge wire do I need...for fridge

For starters - I've never had a "falling out" problem with one of the Blue Sea 12v sockets - especially when used with one of their own screw-in plugs. Pretty solid setup and made for use on a boat. Their design has a built in 10 amp fuse so you basically have to supply a 10 amp capable feed. The ampacity chart shown earlier in the thread is the proper way to size the wire.

For big high amp loads I have used these:

These "SAE" style connectors are pretty handy and available in a variety of wire sizes. Just make sure (if you plan on leaving an open connectionpoint exposed) that the male pin of the ground is the one you will leave exposed! You simply cut the pigtail between the two plugs apart and splice them into the wiring. To provide a bit more weather protection, I take the joints that will be exposed or seldom ever disconnected and wrap the two fully joined plugs with #33 tape.