What are the top 3 USB cables being used today in reference systems?

IMO, one of the most important  parameters of a good USB cable is to have the data lines separated from the 5v power line. The ones I’ve had with separation always sounded better than those that did not.

That being said, I’ve had a $1k+ SR Active SE, a Curious, and a Supra, but my fave has been an Audience AU24SE, and a Verastarr Nemesis, with a slight nod going to the Nemesis.

+1 mitch2 - "the sound of these cables is system and user dependent". 

I have had some low budget and uber expensive USB cables in my system. I end up keeping the Wireworld Platinum.  

Nordost Valhalla, Transparent Cables and a few others who are charging 1000s of dollars for a USB Cable have their marketing strategy working on most audiophiles. Like the previous poster just said if you need to spend this sort of money on a USB Cable something is seriously wrong with your DAC, Setup and your brain.

Where does a Shunyata Venom fall in with these higher end cables? I'm thinking of going with one with my LS50 Wireless and MacBook Air.

I'm a fan of Black Cat Silverstar digital cables. I have two of their 75 Ohm SPDIF cables and recently purchased the Silverstar USB.  Neither are outrageously priced, under $300 but you'll be hard pressed to find any at a discount.  I suppose many people like me find them a very high performer and hang onto them.