I used to own a F-250 Diesel that I towed my boats with so I was spoiled when it came to towing, but we had a baby and needed something a little more family friendly like an SUV so I set out looking for an SUV with the highest towing capacity.
The best thing I found was a 2006-2009 V8 Toyota 4Runner. The 2wd model can tow 7300lbs and the 4wd model can tow 7000lbs which is the same as a Chevy Silverado 1500 Z71 or Chevy Tahoe, but the great part is I get 16mpg in the city and 19mpg on the highway (not towing obviously) where a Silverado/Tahoe will only get 16 on a good day.
They stopped putting V8's in 4Runners back in 2009 and the V6 4Runner's only have a 5000lb towing capacity so it can be hard to find one. I had to have mine shipped across the country because it had to be a black limited edition model with 4x4. The sport and limited models also come with a heavy duty transmission cooling package and I believe the sports come with larger brakes as well.