The top window air conditioner, according to ApartmentTherapy.com, is the Frigidaire FRA086AT7, as of 2015. Reviewers there scored it very highly for efficiency, cooling power, ease of use and price.
ConsumerSearch.com lists three air conditioners as top-rated window units, each for a different room size. The best for smaller rooms is the GE AEL06LS, which is Energy Star-rated and does an excellent job cooling. The best medium-sized air conditioner is the LG LW8012ER, praised for its dehumidifier and energy saver mode. Finally, the best air conditioner for larger rooms is the Sunpentown WA-1211S. Reviewers at ConsumerSearch.com state that it did an excellent job cutting through muggy, hot air.