From The Wirecutter's Great Air Conditioners roundup:
If you've got a small to medium-sized room you want to keep cool this summer, you should buy a LG LW8011ER 8000 BTU Air Conditioner. Priced at $259, it offers a great combination of features, a five-year warranty and enough power to easily cool a 225 − 350 square foot space with some people in it.
If you've got a medium to large sized space you want to drive the temperature down in, you should think about stepping up to a 12000 BTU unit like the LG LW1212ER 12000 BTU Air Conditioner. It'll keep a space up to 550 square feet cool for $319.
I was going to add the $199 Kenmore 75062 to Wirecutter's recommendations, specifically as an option to the the LG LW8011ER. We have two of these LG-rebranded 6000 BTU units in our own apartment and they've served us well for bedroom use. The 75062 is small and slim looking, possibly the least offensive window unit available, while also being very quiet (subjectively speaking, for a compressor driven appliance) and energy efficient.
But it appears Sears has replaced the unit with a new touchscreen model, increasing the price by $70, with the similarly spec'ed Kenmore 6,000 BTU 70062. Overall reviews are fairly positive, but some previous 75062 owners note the new design is missing the handy hand holds and rear grill cover of the earlier generation. Just note, both of these units are meant for smaller enclosed spaces, so stick to a 10-12,000 BTU model like the LG LW1212ER if you're hoping to cool down a space between 350 and 550 square feet.
Both the 75062 and newer 70062 are great for seasonal use in summer, and easy to remove storage during cooler months. Unlike most AC window units, removing and carrying these smaller size models is within the realm of reason (unless you'd like to add them to your Crossfit training), and for several winters, I kept the eyesore of a window AC stored away in storage during colder months.