Newton's most famous work, PhilosophiƦ Naturals, is a must-read for any serious scientist.
Or, you know, just read the whole book.
Newton was also a master of the obscure. Check out his lesser-known magnum opus:
Untitled Treatise on the Nature of Bacon
On the Quintessence of a Good Tea - a treatise on the perfect brew.
On the Invisible Cat - because who hasn't had one of those.