The GekkoScience miners is just slightly better than the original block erupters. It will net you about $0.15 per month, which is more than a dollar per year! The company claims that the device runs completely silent. It works with just one USB port.
The most efficient USB miner ever manufactured is available in limited quantities! The 2Pac features 2 Bitmain BM1384 chips (same chip in S5) and a fully adjustable regulator design that gives you a core voltage range of 550mV to 800mV. Typical hasrate is 15+gh/s depending on clock rate.