I vote for the wooden rocking house. We bought one for my first daughter at her first birthday. It was a smaller one and now 5 years later it still looks like new. Even though both my girls (6 and 2) play with it either by rocking or pull it around by the reins. It also depends on the infants age - if you buy one for a smaller one, the baby will be able to use it around age 1 and will not take up much room. Ours fits nicely between a dresser and the baby's crib.
Thirteen year old - how about a gift certificate to a music store or video store. Usually boys around that age love music and video games.
I am not so sure about the rocking horse. They take up a lot of space. You would need to know if the parents wanted one. Another thing. A rocking horse is far too advanced for an infant. Why don't you get him one of those things that attach to the crib, and allows the child to look and play with it. Or, something like this:
Stumble It!
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