Rob and I bought Breath Palette's grapefruit toothpaste at a cute little collegey gift store in Tempe a few years back. The Japanese company also has toothpaste in bitter chocolate, sweet salt, Indian curry, rose, pumpkin pudding, cola, monkey banana (!) and many more.
Judging by our grapefruit flavor, they are super-lightly flavored and a bit gritty. Fun to try, but not something you want replacing your daily shots of Crest or Aquafresh.