Hobbs Heirloom Fusible (80/20) is the one I use most often, but I also like the non-fusible version, plus Hobbs Heirloom Natural (cotton) and the version with the scrim. I make mostly traditional style quilts or I finish antique and vintage tops and I like the shrinkage and the washability of all these.
If I'm making a child's quilt, I like Hobbs Poly Down (polyester) - it's so soft and silky and seems to stay puffy forever.
I have bought some wool batts and some fusible bamboo blends, but I haven't gotten around to using them, yet.