FWIW, I use a billiard ball for calf work. The tennis balls are just too squishy, and don't dig in there enough. Golf balls are a little too small. And I didn't have a lacrosse ball laying around...
There are some active ROM stretches against the wall that I've used in the past, I think I got them from the NASM bag o' tricks. I'll see if I can dig them up later.