DD is 17.5 mos, and had shellfish probably around 14-15 mos...we don't eat a lot of shellfish here, but DH likes an occassional shrimp cocktail, so, that's when she had it. She had fish waaaaay before then.
DD had peanut butter starting at 9.5 mos, when she grabbed it from me. She LOVES to snack on halved peanuts.
I honestly don't buy a lot of the allergy warnings UNLESS there is a history in the family, or other indicators (eczema, other food reactions, etc.), and there are indications that DELAYING (beyond the normal introduction of solids) may be the cause of some otherwise unattributable allergies. I was actually nervous about the shrimp b/c I'd realized she HADN'T had any shellfish before then, so I made DH give her a very tiny piece.