I have just finished knitting a jacket for Noah, who is three months old. The pattern is one I have used before - Baby Sophisticate by Linden Down (free via Ravelry). It is entirely seamless (hurray!) and uses Aran weight yarn (or in this case, DK used double), so is quick to knit.
The buttons are ladybirds - not very sophisticated, in fact, but cute. And Noah looks extremely cute wearing it. (Actually, it's also hard to look sophisticated when you have to wear a bib all the time to catch dribbles, so I don't think I need to apologise for the ladybirds.)