The most awesomely heartwarming of such counterattacks was when Something Awful released a "Redditbomb". Said bomb contained three core facts: Reddits contained child porn, the higher-ups defended the moderators of child porn sub-reddits, and that the upper elechons of the site tried to defend said child porn. It took multiple Redditbombs for the site to reluctantly ban child porn. fnord.
A counter-offensive against r/creepshots (taking lewd photographs of attractive women without their knowledge) on Tumblr that exposed the personal information of various creepshot posters.
Reddit was also a catalyst for the SOPA/PIPA protests.
Old Shame: Reddit's management have tried to distance themselves from violentacrez as much as possible since the r/creepshots debacle, despite giving him a "pimp hat" award in the past.
Word of God: IamAs featuring media creators, which usually require the celebrity confirming the IamA with a photograph greeting Reddit or some other method.