noglider 

I would advise against a very loud horn or other noise maker. If you really really need it, it's because you allowed yourself to get into an urgent situation. That's a matter of choice. If a bell isn't enough noise for you, you are riding faster than is safe for your conditions.

A good headlight is a good thing.

I like a mirror mounted on my glasses, but many get by without mirrors.

As for repair stuff, bring whatever you are reasonably likely to need. I like bringing wrenches for adjustments, even though I rarely use them. I definitely bring stuff to fix flats, because those surely happen.

The rest are optional. A way to log your miles or route is nice but not essential. Same with camera.