I've tried every litter box type I could find and ended up getting him a giant low sided tub from the hardware store. Anything smaller and he hangs his ass over the edge. I've also tried every type of litter, and clumping clay is the only one he'll use regularly.
I don't think he avoids the litter box, I think he just prefers my clean laundry basket that I was too lazy to fold.
He's also on a specific diet because he's old and gets UTIs easily. I think he just likes being mean to me at this point cuz he's a crotchety old fuck.