This is a super huge pack of simple, line and solid flat style icons, each icon created in full vector and available in PSD and PNG (512×512) for free download.
Total contained 12000 icons in 500 different themes, 3 ready made sizes for Retina version, outline style, filled style, 11 sub-icon addons and addon generator. Totally free and open source for personal use. I think you will need few days to go through all the icons xD.
Thanks iconShock who brought us this shocking icon set for free, happy sharing guys! Enjoy.
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Cost: FREE
Requirement: .PSD, .PNG
Source: Read more about this ultimate line and solid vector icon set