What kills your GB the fastest on Air 2

You tell me.

Given your user name, is it you???

if by kills you mean take up storage then imho

big games -> videos -> general apps -> music and photos

in that order

Full length HD movies will easily be amongst the very largest files people store. Their own videos another. Some games can be quite large ( e.g. Strategy board games). Music can take a surprising amount of storage, especially if you rip CDs at very high sampling rates, or purchase enhanced albums with video content.

depending on how you use your device, apps may be a big part of used storage, but that will vary a huge amount given people's varied things they use their device for.

Gigabytes of what? Storage space? Data usage?