This Portal 2 turret stands 14.5" tall. It's soft. It's cuddly. And it talks.
Due out in mid-December, it's an officially-licensed product available at ThinkGeek, and will go on sale for only US$30. While the plush's product listing doesn't specify which phrases the little darlings will utter, they do say the turrets will know all "the phrases all proper sentry turrets should know".
While Portal devotees are the initial targets, I can see a lucrative secondary market opening up for people who make internet videos about cats.