I made a list from the beginning of this thread till now. I collected everything depending on GPU type, H/s and W. Almost all listed cards have modded bios or clocked to best Hash/Watt ratio.
I hope I got everything right and of course everybody is telling the truth

listed in order of efficiency:

7950/280      290-300H/s @ 200W
7970/280X    300-310H/s @ 210W
290/390       395-400H/s @ 260W
290X/390X    400-410H/s @ 260W
Fury/FuryX   450-460H/s @ 275W
RX 470        290-300H/s @ 110W
RX 480        300-310H/s @ 90W
Nano           450-460H/s @ 175W