PNG SVG MORE
Signs & symbols
Glyph
Miscellany Web icons
approve, Check, list
Black
448x512
PNG ICO ICNS SVG MORE
Mixed
Simple files
success, Accept, Check
512x512
Avatars & smileys
Human Movement
pose, monkey, listen
gandhi, good, monkey
pose, Behaviour, good
Business & finance
Free Misc Icon Set 1
good, Check, ok
PNG ICO ICNS MORE
UI
Round UI Buttons
ok, tick, yes
OliveDrab
Math & Business
creative, sign, true
506x512
Very Basic. Android L (Lollipop)
done, check mark, good
Free basic
Accept, checkmark, Check
DarkSeaGreen
PNG MORE
Mobile apps
Free Retina Icon Set
ok, Face, pleasure
60x60
24x24 Free Application Icons
good, mark
LightGreen
24x24
Windows 8 metro style
good, Decision
DarkSlateGray