From your experience, what are the best toys for a 3 month old?

My 3 month old seems bored with his toys so I need new ones for him. He has the Baby Einstein Play Gym where toys are suspended all around him and he bats at them. However he seems ready for something new and I want to ask you guys first what your children REALLY loved, both for having fun and for helping them developmentally.

Is a 6 mo old to old for a baby gym are are they usable until a year old.I know they start crawling soon after?

I know babies start crawling soon after 6 mos but do you think she will stay on her back long enough to play with it. I am looking at the Baby Einstein Neptune Ocean Adventure gym. She absolutely loves to grab and fiddle with things since the age of 2 mos.