I’ve got a selection of Smart 1W LED’s that have lasted for an eternity. Great little lights that aren’t the most waterproof but can be easily dried out & run on AAA’s. For a tenner I like these a lot. Comes with a versatile bracket that can be mounted on the seatpost or the back of your lid. I run two of these.
Lezyne Strip Drive. Solid light, rechargeable & has lasted about 4 years & still going strong. Downside is that the seatpost mount has it facing a downward angle. Still visible but not optimum.
MagicShine SeeMee 200. The brightest light & the most visible I’ve owned. Tons of modes including a brakelight function that I don’t use & a bright LED that illuminates the back of the bike when the ambient light is low. However! I bought two of these last year at Christmas. One of these failed after six weeks & was quickly replaced under warranty by something that looked decidedly 2nd hand. Then the other failed & was replaced after a few emails with a new one. Then the first replacement failed & I gave up chasing as my emails were going unanswered. Life being too short etc.
I’ve bought Mrs Davesport a set of Bontrager Ion/Flare 200’s for Christmas so I’ve got high hopes after reading the reviews. As yet; untested.