Bobcat. And it may be legal where you live depending on various licenses and whatnot. They do, however require a very particular diet and a lot of room, and are not good with kids or strangers. Think of them like a protective dog, but with claws (2x1d2) in addition to the teeth (1d4)...
Only that both links redirect to us.ncix.com
Also, modular isn't super important if you have plenty of space behind the motherboard tray for cables. It's also significantly more expensive.