I redyed some elderly black linen shirts, they now look new. Also a lovely swirly chambray skirt. I dye my bedlinen on a fairly regular basis, also towels, as they start to look tired. DBH says he has to keep moving, in case I either paint him or dye him.
Old faded t-shirts, but if you have spilt bleach on them or fat, you have to be prepared to add a little embroidery or applique. It's only worth it if you really like the t-shirt.
I even dyed a suede jacket once. I was going to a spring wedding, it was a smart beige jacket but it didn't look wedding-y enough. I used cold water dye and dyed it deep pink, it was lovely. That got me really started, and suede shoes and boots were next. That was back in the days of buying shoes and boots in non-sensible colours, of course! I still have a pair of pink suede kitten-heeled shoes that had once been cream, they are still going strong.