I am very fortunate to have a lot of jewelry~I worked for 25 years with the last 10 in admin. So I had to have all the right pieces ;-/ Nevertheless, my very favourite pendants are among my most simple ones.
~I have the Tiffanys peace dove in sterling silver. It was I believe a limited edition from the Paloma Picasso line that DH got for me a few years back for Mothers Day (with a little direction from DD). It's so prescious and I wear it a lot.
~Last Christmas my kids gave me a pendant and chain from Red Envelope. It is 3 little pearls, they can't be more than 2-3mm with 2 sterling arms coming down in a tear drop shape as if to protect the pearls. The kids said The 3 pearls stand for the two of them and me, and the arms are Gods protecting us!! I was floored when I got that one.
~And my last "fav" pendant is a Helen Ficalora set I have had for several years. I actually bought it for myself after my dear Mum passed away. There are two discs; one with a cut out heart, one with the word faith engraved on it and then a tiny little flower with a tiny diamond in the center. That one is yellow gold. I love it and wear it very often.
For all the expensive ones both solid goldm platinum and gems, those three in their simplicity and spirituality mean more to me than anything.