I'm sure my style, or lack there of, breaks every rule mentioned on this thread. Like NKOTBIE, I detest the V-neck, no matter what kind of shirt. But I always wear a T-shirt under polo's, under sweaters, under button-downs, under everything basically. Mostly cause at some point in my youth, it was comfoartable, and now it always will be. I hated undershirts for a very long time, cause they always shrunk in the wash and never fit me after one wear. However, I discovered the soft world of jockies, and now I can wear undershirts again, cause they fit and they feel good. But I still tend to wear them only with dress shirts. Cotton T-shirts will always be my undershirt of choice. It's all about comfort to me.