I've covered a few Android icon themes from Ryan Kelly before, however recently he updated Hexacon to v2.0 and it's easily one of the best Android icon theme packs out there.
Hexacon features over 700 unique icons and Ryan has gone through to design them all with some incredibly fine and minimal detail. Unlike your standard round or square icons, the Hexacon icon pack as that name suggests is made from hexagons. It instantly makes itself very unique compared to other themes. When used with Nova Launcher, the icons appear in a honeycomb look which looks pretty stunning.
Hexacon is available on the Google Play Store at 50% off the original price till the 22nd of September.