LED rear light
Cateye Omni 5 rear light
Cateye make some great value lights that perform well, and the Omni 5 (or TD-L155-R, to give it its catchier name) is one of them. There's a lot to like about this rear blinky. It's not the most powerful or the sleekest, but it's a great all-rounder.
Light & Motion Vis 180 rear light
We reviewed Light and Motion's Vis 180 a couple of years ago and liked it. Since then, it has shed some weight, gained even more lumens and still costs a lot.
The Vis 180 is a (micro)USB rechargeable rear light that is seriously bright, and is visible through 180 degrees. It achieves this through two dedicated amber LEDs pointed to the sides, as well as obviously the main red rear facing light.
Knog Boomer 1 LED Wearable Rear Light
The Knog Boomer Wearable is very similar at first glance to its big brother, the Boomer Rechargable, being a brash, bright LED illuminated rear light. But this is where the similarity ends, since for one thing, the Boomer Wearable is battery powered (using 2 AAAs), and if you're wondering about that name, it IS also wearable.
Moon Shield Rechargeable Tail Light
Unless that nice Brian Cox has led me astray the mighty Moonshield rear LED should really be called the Sun Shield, seeing as the Moon only reflects light, it doesn't kick it out in great strobing pulses with a disco flash.
Exposure Flare rear light
The Flare is the self-sufficient rear light from Exposure, a development from their Red-Eye rear light that sucks power via a lead out the back of one of Exposure's powerful Joystick off-road lights. The tidy little Flare runs off a single CR123A battery - a squat camera battery to you and me. It pushes out a bright 75 lumens of red light via a Seoul P4 LED. Exposure say there's 9hrs of constant light to be had with a disposable battery and 3hrs with rechargeables, or 22hrs and 8hrs respectively in flashing mode.
RSP Mico Flexilight rear
Waiter, waiter, there's an RSP micro flex light rear in my soup...Keep you voice down sir; they'll all want one. Superb weather seals, shapely, tactile design and impressive power to size ratio, the flex light ranks high in my back up lighting hall of fame and should be of particular interest to winter time trialists or road racers who don't want to find themselves cheated by the sudden onset of darkness.
Waterproof rear lights
Do they exist? 
So far have killed 3 Flea lights (originally won on here via Schwag grab) - Madison stopped responding to emails sadly, so lifetime guarantee not up to much there. 
Which is a shame because they were fab lights - just not waterproof.(Front light is fab and appears to be waterproof - maybe I shouldn't say that probably kiss of death 
)
EDIT: actually that is 5 Flea rear lights die. I had three sent back to madison, and I've got two knackered ones on my computer desk
Killed a Lumicycle rear light - which again surprised me.
RSP Tourlite LED rear light
Bigger in some cases is certainly better and very apt when describing RSP’s new Tourlite. Designed to bolt directly to the rack platform, it might be portly but the half- watt LED flanked by two smaller units and integral reflector pack a mighty punch. Raleigh claims it’s visible from a mile and friendly acquaintances suggest this is no idle boast.
Blackburn Mars Click tail light
The Blackburn Mars click is very hard to beat in terms of build quality, burn times, output relative to size and good old fashioned value for money.
Models with greater LEDs and larger surface areas are better choices for tag-alongs/trailers but prodigious peripheral visibility, brilliantly executed switch and universal bracket mean the Mars is a delight to use and won’t spoil the clean lines of sporty audax/winter training bikes.