My preferred, indeed my almost exclusive form of masturbation is nipple play. I have been blessed with very sensitive nipples. I have always been able to have orgasms from nipple stimulation alone, but about eight years ago I discovered that I could also have multiple orgasms this way, without touching the penis, and that these orgasms were more intense, whole body orgasms. I often have 8-10 orgasms in a day, as many as 12 in a single session. This has made my penis a bit player. It gets more intense sexual feelings from iindirect stimulation through the nipples than by being stroked. Only sucking is better.
I have a Yahoo group dedicated to the topic of nipple orgasm. http://groups.yahoo.com/group/nipple_orgasm/