Graffiti may not be a welcome form of art in many places. But, I doubt if anyone would object to virtual graffiti in an iPhone app.
Graffiti Spray Can (iTunes App Store)
Graffiti Spray Can is a free app that lets you create graffiti on your iPhone or iPad. The app provides numerous tips/brushes and stencils/fonts. The recent 1.7 update supports iPhone 4’s Retina Display, provides new HD backgrounds and three free music tracks.
You can share your work of art in a variety of ways including posting it to GraffitiSprayCan.com’s Wall of Immortalz, email, Facebook and Twitter.
You can remove ads in the app through a 99 cent in-app purchase.
Graffiti Spray Can 2 is also a free app and works on the iPad.