Obviously it's all personal preference. I really depends on how luxurious you want to "live" while on the road.
To give some perspective on Dangerbus' post, I'll comment on the items as they applied to my 65,000km, 22 month drive from Alaska to Argentina.
I very much subscribed to the less-is-more philosophy.
Essentials/Must Haves
Vehicle- 

Agree 4x4 is not a must, as anywhere you want to go has a road.
Awning-
I didn't have one, and actually can't think of a single time I wanted one.
Screens-
I got bitten by bugs less than a handful of times, and I would just dive into my tent. No biggie.
Fans- 

I had nothing.
Water- 

I just had a 20L plastic container, it was find, and easy to fill for < $3 in every country.
Fridge/Ice-
I had nothing, though I did kind of want one just for "luxury".
Extra fuel-
I had nothing, and ran out of gas once in Argentina.
Propane/Cooktop-
I had an alcohol stove, which was fantastic. You can *always* buy alcohol at drug stores in every country.
Air Compressor-
I had the cheapest 12V compressor money can buy, and used it once, because I couldn't be bothered putting on my spare tire.
Tow Strap-
I had a length of old rope, and used it once or twice to pull other people out of ditches.
Recommended
Good solar setup-
I had nothing, the Jeep battery was perfect for charging batteries/laptop.
Grill-

I had Nothing
jumper cables-
Had 'em, never used 'em. Push start was always an option.
portable shower-
I Had nothing.
sand ladders(depending on your offroad use)-

I Had nothing.
spanish/local languange-
Agree, very nice to speak more Spanish. I took lessons in El Salvador.
Completely Unnecessary
gps/spot/phone- 

Agree - not needed.
Wetsuit/Snorkel gear-
Could be fun, there sure are a lot of beaches in CA.
4wd- 

Agree.
RTT- 

My ground tent was fine.
Sink-
Agree
Backpacking Tent- 

I had my one and only tent, which I used for backpacking.
Weapons-
Absolutely don't want one.
-Dan