Cycling tips did a good story on day time lights.
I've used this Cateye for a couple of years. Excellent light, long lasting, smooth design
I have nearly drowned on the road several times but never had a water issue with this light. Battery has never died on 5-7 hour days on slow flash. Quick flash would probably result in a heap of abuse from cyclists and drivers ;-)
I've got an older Cygolite Hotshot Pro. Its 80 lumen which they no longer make but have now gone to 100 & 150 lumen tail lights. Absolutely brilliant light for day time running. I've had many riders comment they can see it from a huge distance back. Probably to bright for night riding if you have riders behind.
Smart Superflash is a cheap but good strong light, runs on rechargeable AAA's and you can stick a couple of spare cells in the saddle bag. I don't like the built in battery types because they're easily forgotten about and are likely to be flat when you need them.
Any knog taillight. Now that they're supplying replaceable mounting straps, you can't go far wrong with these. Totally waterproof - unlike my Cygolite and battery lasts forever - to the point where I've forgotten that it does need charging occasionally.
I second this. I have a Knog Blinder 4 (I think they're called Four Eyes now) and it's super easy to mount, very bright and sturdily constructed.
I thought I would try another brand when I bought a headlight recently, and I honestly regret that I didn't buy another Knog. It's aussie too!
At only 44 lumens, the Knog's are no where near bright enough for day time riding.
They have good optics though, which is just as important as the rating in lumens.
If anyone already has a Blinder, I'd be willing to put my 80 Lumen Cygolite up against the Knog to see which is brighter.
Thinking about it, seeing which light is best for day time running wouldn't be a bad experiment. Get a few tail lights together, set them up in the parklands somewhere and see which one's stand out the most at 50 meters, 100 meters, 200 meters etc.
Well , , it looks like I've really started something , , a tail light "shootout". ha ha !