The Reeves deadlift is a combination punch of upper-back strength and total arm and hand strength. People who think a snatch grip deadlift is the ultimate upper back builder haven't yet performed a Reeves deadlift.
To do a Reeves deadlift, load the bar with standard 45-pound plates with the flat side facing in. Standing in the middle of the bar, grab the 45's with the fingertips of your outstretched arms and perform a standard deadlift.
Most big deadlifters would agree that one of the best ways to build a big deadlift is to augment your deadlifting volume with more volume. One can only handle so much deadlifting (although it's probably more than you think you can), so the real key is to increase the variety of ways in which you pick shit off the floor (PSOTF).
Adding the Reeves deadlift to your training, which is primarily limited by hand and arm strength, is a way to double or triple the number of reps you have of PSOTF.