That's really hard to say, since my commuter is a frame up build and nothing really stands out. The accessories that come to mind as the most used or handy would be the "Cree" headlight from Amazon (about $15-$20 currently), sunglasses, and assorted generic jerseys. I couldn't do without the jerseys for the pockets. I have some neoprene shoe covers that I like and which look pretty good, but honestly the DIY ones are more effective.
Wheels, I really like my Vuelta Corsa Pro wheels and would do it again but I'd probably choose the Lites over the Pro's.
Most everything else is DIY: fenders, tail light, mirror, bar and stem mounts, frame bag, tool compartment.
I'm not as newbie as all this probably sounds, not being all that excited about components and accessories - I'm at about 94% total commutes by bike the last five years (19,000 miles), and exclusively by bike for a couple more before that (with a department store bike) so I do have some experience.
Last edited by wphamilton; 04-21-15 at 03:40 PM.