I like Arm and Hammer Essentials Kitty Litter - it's the best non-clay litter I've found. Baking soda sprinkled in the bottom and sprinkled when you scoop also helps. I got my 2 cats from a shelter - they were older, not kittens - and they smelled at first, too. One more so than the other, I thought she must be sick and could hardly stand to have her in my lap. They also never cleaned themselves which I thought was weird because my previous cats spent hours self grooming. So I bought deoderizing kitty wipes and just brushed them and wiped them like once a week. After they settled in, like a month later, they started self grooming. My theory is that when they were anxious at the shelter and when they first came to me that grooming went to the low priority list for them until they felt safe or maybe, because cats are all about their environment, maybe they wanted to be surrounded by their own scent as a part of settling in. Give it some time. Both my cats are fine now, they sit in the same bed and groom each other, it's so cute.