I heard good things about iSwifter and Skyfire, however, IMO they are both pretty bad browsers, the flash is slow, but it works. The rest of the browser is just sluggish and the UI isn't too great either. I find the screen has a lot of unnecessary clutter, unlike with Safari.
Although, I used to use Mercury Pro, it doesn't support flash, but it has private browsing (birthdays ... not porn
) and fullscreen along with some other useful features like gestures. But still, safari remains my browser of choice.