I've been looking through some of the stuff and I must say I have not seen many GOOD big tit stuff. And when I say big I mean as big or bigger than the girl they're attached to to.
Updated
Posted under General
This topic has been locked.
Terms of Service
By accessing the "Danbooru" website ("Site") you agree to the following terms of service. If you do not agree to these terms, then please do not access the Site.
[...]
Prohibited Content
In addition, you may not use the Site to upload any of the following:
[...]
EDIT: I got TOS-sniped!
(not as large, but w/ several other factors, similar TOSing, and for teh lulz: post #369258)
The ones tagged with gigantic_breasts will be the biggest ones you will find undeleted and TOS compliant here at Danbooru.
As bigger ones would go against the Terms of Service, as RaisingK quoted.