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Get a full rear fender, it'll keep a lot of that sand-like grit from the rainy roads off of your drivetrain and your drivetrain will last longer. The longer a front fender is, the more useful it is. A long front fender with a good mudflap will keep spray off your feet when the road is wet, but it's not raining at the moment. It's nice to be comfortable riding in that road conditions at least. It's also nice to be able to ride in and risk a possibility of rain for the ride home and not sweat it. I'd swear the weather forecasts are always pessimistic, if I let any chance of rain keep me from riding it'd happen a lot less. For a three mile ride, fenders can help you stay in non-cycling specific clothes, it's a bummer to get caught out in an unexpected rain and show up with a skunk stripe of road mud and grit down the back of your clothes and pack.
A) bell
B) Airzoundz horn
C) reflectors
D) lights
E) tires
F) bar ends
I'd either skip reflectors or get lights that incorporate them. If skipping them, replace them with reflective tape. There's a thread here "making your bike glow down the road" with great examples of this like:
http://www.bikeforums.net/showthread...-down-the-road
For the frame and fenders I get that effect from "Peterson Manufacturing 465-4K Red/White Reflective Marking Tape" that I get from amazon, but I suspect any truck stop sells it as well. It's still going strong after two years commuting almost every day in Seattle.
I find having a bell essential. There's a reason it's actually one of the few bicycle specific laws in a lot of places too. It's a nice alternative to shouting and sometimes more effective. IMO, it's worth paying a bit more for a quality bell, my old favorite for the past 15 years, The Temple of Tone, just got dethroned by the Crane Suzu. I bought a black painted Suzu for my girlfriends bike and was shocked at how superior the tone is on it. It penetrates. Despite having a Temple of Tone for each of my planned builds in my stash, once I heard hers, I had to order a Crane Suzu for my commuter, it's so good.
If you are considering the flash light solution, you can get a nice T-6 Cree with two batteries and a charger for about $16 delivered from ebay. With a two dollar flashlight holder you can mount it on the handlebars and quickly take it with you. I picked up an extra pair of batteries for mine online, and now I'm all set. I'm seeing a lot of different options for these on ebay right now, keep in mind that you want it to be balanced and have a smooth handle to go into the clamp and stay there. Look through them for a compact light, plastic cased, with a smooth barrel. Mine is SUPER bright! It's got a flash mode, but it is so bright that it would be punishing to others on the road, lit up solid and aimed slightly down it's unmissable but not eye-assault. I actually run a Cateye Reflex combined reflector and light as my front flasher, day and night. That one just stays with the bike.
You can combine a rear reflector with your rear tailight, Cateye's Reflex model nicely combines the two functions, and I think gets overlooked by thieves because at first glance it appears to be a standard reflector. Often fender mounted tail lights combine the two, certainly my PDW Fenderbots do, and I like the Spanniga Pixeo I put on my girlfriends bike even better. The clear upper housing actually fills with red light like a lantern, it has real nice side visibility.
I found the reflective tape did pretty good for the rear view too:
That's the seatstays and also I pinstriped the fenders in reflective tape too (makes a nice outline of the tire from the side too, like having reflective sidewalls), pedal reflectors, and the reflector on the Portland Design Works Fenderbot tail light, in the flash of my phones camera.
All the above I consider minimal safety equipment for riding (along with a a helmet mounted mirror).
If you wait on replacing the tires, pump them up quite a bit for city riding (if they're full on knobbies, I'd probably overinflate them some). Tire liners (like Mr. Tuffy's) can extend the life of tires along with providing flat protection. I can't recommend a tire in 1.75", I really like 1.5" tires (Vittoria Rando Pro and Panaracer T-Serv). Lately I've been eyeing the 2" Big Ben tires, I'm going to have to come up with different fender solutions if I go that route though, the only 1.75" tire I liked (Continental Town and Country), they changed the composition of and discontinued it in 1.75, and it just isn't the same tire in 1.9", although it remains popular with police departments.
For a good, cheap bar-end option, I actually really like old school MTB long bar ends. Bicycle co-ops and recyclers have these for a few dollars and new ones can be had for not much more. If you actually spend a lot of time in them you can wrap them. I like them for a place to rest my hand as well as for climbing. I like ergo grips too though. I have one old MTB that has them right now and I'm always surprised how much I use them when I take it out for a spin.
I have some like these:
(Image borrowed from this thread)
http://www.bikeforums.net/showthread...ound-Road-Bike
I'm actually hoping to cut and weld an angle into a pair like this so that they align nicely on a non-flat handlebar soon, because I miss these and want them on my commuter.