My son loved the wave drum at Stay and Play so we got him one for his first Christmas and he still loves it now at 21 months as does his four year old brother.
He generally enjoyed simple, easy to hold musical toys as soon as he could sit up.
B. One, Two Squeeze blocks (on Amazon) are great as well. For little ones they are great teethers. As they get older they can enjoy stacking them up and knocking them down or watching a parent do it.
My older son loved Sophie the Giraffe, my youngest was a bit indifferent though!
My youngest loves taggie toys, my oldest wasn't keen. If your child likes taggies though they can be a good stocking filler. If you look up Jellibabies she does every kind of fabric and personalisation you can imagine.
Toy keys seem to be a hit with every baby, teether keys are a good stocking filler.
Board books are always good, 'That's not my.....' range is really popular. Also things like Dear Zoo, Where's Spot, Peekabook books and ones with photos of babies in.
My youngest liked toy cars really young, so maybe a baby friendly toy car would be good?