I have been using Mercury browser a lot. I like that I can scroll down quickly something Apple never added to Safari and the ad block works okay. Not as good as on a computer but it is better than nothing.
chrome with occasional safari use; chrome has become my default since it seamlessly syncs between my idevice and pc; something safari can't do with a hybrid device environment
Just Safari. Though I don't use the browser all that much on my iPod. I prefer to use a dedicated app whenever possible, since they're better optimized for the small screen.
Mercury to get serious job done. Syncing is unmatched. Adblock is OK. A tad slower, but additional features and shortcomings adressed from Mobile Safari make it a no-brainer.
Will never use Chrome from its utter lack of respect of privacy by its parent company.
Safari, mainly because it's default. I had Chrome at one point, but I never put it in my bottom bar, rendering it useless. I don't have any issues with Safari, so I'm fine with it.