I recently tried, and am now deeply addicted to a citrus variety called Cocktail fruit or Cocktail grapefruit (it's not a grapefruit at all, but a hybrid of a pomelo and a mandarin orange).
The Cocktail fruit look like a grapefruit, but are a the color of limes, at least those that the trees produce early in the season. Later in the season, they're yellow and are indestinguishable from grapefruits (until they're cut open or tasted, anyway). Right now we must be in the middle of the season, because some are green, some are yellow, and some are splotched with both.
The taste is incredible. They're super juicey, and sweet. The main flavor is alot like a not-very-tart lemonade with a trace of grapefruit and/or orange (but just a trace). There are quite a few seeds, but the fruit is easier to peel than a typical grapefruit (not quite as loose-skinned as a mandarin orange).
I peel it like an orange, but the membrane covering the sections can be a bit bitter, so if it is, I will pull it off. It pulls off very easily compared ot most citrus fruits). There are quite a few seeds, but the taste is worth it.
If you're familiar with Ugli fruit, the taste is very similar, though the peel is not as loose. I thought that Ugli fruit was a cross between a grapefruit and a tangerine, but learned that it's more likely a cross between a pommelo and a tangerine. Which explains the similar flavor.
Ugli fruit are twice the price, and I don't believe the flavor is any better. In fact, unlike Ugli fruit, I haven't yet had a Cocktail that hasn't been very sweet and very juicy.
I was so impressed, that I bought a couple dozen of them to include in family Christmas gift baskets (along with my homemade jerky).
It reminded me of the association I've always had of citrus fruits with Christmas time. Often oranges (and candy) were in our Christmas stockings - and our grandparents would tell us stories of getting oranges and candy in their stockings, but that oranges were rare and expensive and prized as much or more than the candy.
My dad would always get my mom a HUGE fruit basket for Christmas (and one for Easter,too) and we'd all get excited about it. I'm only 43 - so it wasn't as though fruit was rare, but my mom was very practical when she bought fruit during the rest of the year. She always bought two or at most three varieties of fruit at a time, so having a basket of six to eight different kinds of fruit in the house was a really big treat.