Filtered pics are all the rage these days. All the kids are doing it. There's some newfangled app called Instagram or something that's a big hit on iOS and is eventually coming to Android. There are numerous effects applications already available for Android.
HTC Sense 4 and HTC One add a number of filtering effects to the camera app that you can preview and apply in real time. You've got 15 effects from which to choose (16 if you count vanilla.) They are:
Depth of Field
Set the effect using the big blue button in the camera app, and you're good to go. We'd prefer to have an option to simultaneously save an unfiltered version along with the filter effect, but it's not a deal-breaker.
We've got a full range of examples of all the effects in a gallery after the break.