1. Nvidia GeForce GTX 1070

Low power draw, high hash rate

Core Clock: 1,506MHz | Memory: 8GB GDDR5 | Memory Clock: 8Gbps | Power Connectors: 1 x 6-pin | Power Draw: 150W | Outputs: 3 x DisplayPort 1.4, 1 x HDMI 2.0, DL-DVI
high hash rate of around 30 mh/s

2. AMD Radeon RX 580

AMD's GPU is a mining winner

Core Clock: 1,257MHz | Memory: 8GB GDDR5 | Memory Clock: 8Gbps | Power Connectors: 1x 8-pin, 1 x 6-pin | Power Draw: 185W | Outputs: 1 DisplayPort 1.4, 1 x HDMI 2.0
excellent hash rate of 29 mh/s

3. AMD RX 480

An older GPU, but still great at mining

Core Clock: 1,120MHz | Memory: 8GB GDDR5 | Memory Clock: 8Gbps | Power Connectors: 1x 8-pin, 1 x 6-pin | Power Draw: 150W | Outputs: 1 DisplayPort 1.4, 1 x HDMI 2.0
decent hash rate of 28mh/s

4. AMD Radeon RX Vega 56

Punchy graphics performance above its weight

Core Clock: 1,156MHz | Memory: 8GB HBM2 | Memory Clock: 800MHz | Power Connectors: 2 x 8-pin | Power Draw: 210W | Outputs: 3 x DisplayPort 1.4, 1 x HDMI 2.0

5. Nvidia GTX 1080 Ti

A brilliant, yet expensive, GPU for mining

Core Clock: 1,480MHz | Memory: 11GB GDDR5X | Memory Clock: 11GHz | Power Connectors: 1 x 6-pin; 1 x 8-pin | Power Draw: 250W | Outputs: 3 x DisplayPort 1.4, 1 x HDMI 2.0
hash rate of 32 mh/s

source: http://www.techradar.com/news/best-mining-gpu