I like opals, but my most favorite are moonstones, I like the face that they come in several colors and they look very nice with any color they are placed against.
I love Diamonds, but Rubies are my birthstone (wow, expensive taste!). lol But, I like Opals too as my husband and I were married in October. I have an old Opal ring that was my great-grandmother's. My mom's cousin (we're still not sure how SHE ended up with the ring), gave it to me for a wedding gift to wear as my "something old." I about cried when I opened the gift.
I love them all! Seriously, I do love gemstones. My Mother and I go to a big gem show every year.
I think my top favorites are Sapphires (DH's and my birthstone), diamonds, opals, tanzanite, pearls, and pink tourmaline. Or better yet, multi-colored tourmoline with pink in it. At last years gem show they had some earings made from that, and I just droooled and droooooled over them. And wished for more money. Pearls I love because they are my Grandma's favorite. They never fail to make me think of her.