Kneeled sounds wrong to me; leaped and leapt are almost interchangeable; I think I have a preference for dreamt, but whether I say dreamed or dreamt I always wonder if I've said something wrong. For the rest of your list, Candy, I would always use the -ed version. I don't object to the -t forms, nor am I uncomfortable when I find them, but to my eye and ear they seem… archaic, I suppose. They just don't live in my immediate environment.