I too like Merino wool and silk. It all depends on what I am about to do though.
For my amigurumis I mostly use Catania cotton yarn and its really beautiful to the touch.
Some works are better done with baby yarn which is definitely the most lovely to knit and crochet with.
I love merino wool and baby alpaca. And lately, Ive started using CoBaSi for summer-weight socks - its got elastic in it, and it wears like iron. Even my better half hasnt been able to wear holes in socks made from CoBaSi. :)
I like to knit with many different types of yarns. Weight-wise and lately its been fingering weight - Ive been knitting shawls. But I also use a lot of worsted and DK weight. Fiber content-wise I like merino, bamboo, silk, and cotton blends. I gave up on most cashmere yarns because they are too expensive and most weights pill, which is a nuisance. Right now I am knitting a shawl of a linen/modal blend. It will get softer with each washing so as soon as it is off the needles, which will be in another row or two, Ill wash it!