I like knits - yes, I'm crazy. and.... I did recently get into quite a big fight with some really beautiful performance wear. Probably ruined it. I had to send it off to Mom so she could salvage it.
I would have to say cotton blends.....only because I'm too chicken to wrestle with anything else. I like fleece too, but I never know what to do with it.
Fleece of course is more of a winter fabric, but I have 5 kids with 4 of them in competitive sports, so there are a lot of sweat pants flying around this house lol!
Sweatshirts can be excellent pieces to repurpose and upcycle. My youngest boy is 8. He recently made a small throw pillow for his bed, out of his favorite yet too small sweatshirt. I helped him cut it out etc, helped him with the machine, but he did most of the work. He loves his GAP Hockey pillow!