I really liked the "mobile home" unit - was a heat pump - I had in my house in Tennessee a few years back. Everything was self contained, it came charged with refrigerant, all I did was wire it up, hook up the two large ducts, seal the entry to the crawlspace, and it was chilly in there. I picked it up at a truck freight terminal and placed it with my tractor bucket on the concrete slab.
The duct work was not ideal for superfine distribution and its a large metal box outside of the house, but for simplicity and function, it was awesome. It got chilly as soon as I fired it up.
I think it was a 2ton or 3ton unit, forgetting the details now, but I just matched the old janky AC that it replaced.