I usually suggest the Kala Travel ukulele as a first instrument, if you can afford it. They always sound amazing for such a thin body, are well set up and intonate well too.
If your hands are chubby and / or you mostly play guitar, think about the tenor size. 17" tenor scale instead of ~15" concert scale length makes it much easier for guitar players. You can find more detail here:
http://www.boiseukulelegroup.com/uke-basics.html