DS (8 mo) likes anything that's not a baby toy. So, as long as he won't hurt himself and as long as I don't care if it gets drooled on or dropped, he can have it. He loves my keys, wooden spoons, the pasta strainer, the arm to our rocking chair, an old toothbrush (well, not old, but he took it over so I had to get a new one). He really, really loves my phone, but I'm not ready for him to destroy it so I tend to keep it away from him.
Mama Bear , Papa Bear and Baby Bear (8/11)
For what it's worth, I don't think keys are considered safe for babies because they may contain lead -- see http://www.mothering.com/community/t/469226/psa-keys-contain-lead-dont-let-babies-play-with-them .