Whether or not it's CW perhaps the List of accessories and training for commuting question should become several good answers:
- Rain jackets for commuters
- Fenders for commuters
The best might become blog entries.
This question has two major problems. Why I think it should be closed:
As written, this is a list question. To people saying that this should be a community wiki question, please do spend some time reading this blog post on the Stack Exchange blog and you'll see that CW isn't a quick fix for open-ended chatty questions like this: The future of Community Wiki. However, I do recognize that the two answers that have been posted are good ones that go into detail.
Also, this question is a duplicate. In the early days of the site, we opened the question What's your most useful cycle accessory?. We later opened What are the utmost important things to bring on a ride?. While the first question is more general, and the second is more geared towards day rides, this question doesn't bring anything new to the party. It mentions commuting, but doesn't bring up any concerns specific to commuting; this answers to this question could easily be answering ether of the two earlier questions.
If this is going to be left open:
I suggest the question be edited a bit more to indicate why it's specific to commuting. This will differentiate it from the two other "accessories" list questions we have open.
Also, while we haven't seen any answers consisting entirely of "you should being a [thing]", I also suggest the mods protect the question to prevent this possibility. (This is less of a big deal, since those answers can be turned into comments as they occur, but it'll save them some work.)
(As I posted earlier, I would prefer we close this, but I understand that many will disagree. Have posted this as a separate answer so people can vote on it separately.)
I think that the intersection (common subset) of two topics lets an answer be more focussed and interesting: not "Rain jackets?" and not "Commuting?" (which are too broad), but "Rain jacket for commuting?" is precise, and could generate (or has already generated) an interesting answer of a few paragraphs.