I tend to use something similar to the genre I'm creating. I tend to create a lot of different genres so for example:
Progressive References: Many guys here but id probably stick to Prydz or Deadmau5 stuff because they are punchy yet dynamic.
Deeper Progressive stuff: Guy J's music is a fine example of Deeper progressive music to reference.
Techno / techy stuff: Usually stuff by Mark knight, Dosem or maybe Hot since 82 tracks. They are engineered in a way to sound really big in clubs. Crisp drums and bass.
Also an artist I will throw in there for reference tracks is Joris Voorn. His stuff is really nicely engineered. Great reverbs and space, great drum programming and great dynamic variation to his music. Everything is so well balanced.