Far and away my favorite and most used app. I think I have most all the Hipstapaks available.
Another fantastic app for photography is Snapseed. The best photo editing tool around!. Takes a while to figure it all out, but WOW at the results you can get!
Slowshutter (photography) - takes motion blur images for you -- light traffic light trails, etc.
Manga -(photography) takes a photo and instantly transforms it into Japanese anime art - but black and white only. Like a pen and ink drawing. You pick a background, then take the pic and there it is.
The Beer app...you can add all the beers you've tried, rate them, write reviews, take photos and even share to a beer community. Great way to track what is and isn't good when you hit the distributor.
Showtimes Movies ... lists all the current movies and times in the area based on your current location. Great for a last minute "let's hit a movie after dinner" ideas.
Starbucks -- just downloaded this one when I saw someone pay at the register by showing their phone. You can load a card on your phone via paypal or a credit/debit card, then pay by tapping at the store based on your location! You add a list of your "favorite" stores and it holds that info for you.