I use a Lezyne 1600 XXL light. It’s a bit on the chunky side, but the battery lasts forever. This has come in handy on mountain roads in the middle of nowhere, and allowed me to ride all night. Lezyne has a lot of different mounts and accessories available, the light can be controlled by a remote switch, and with a smart phone app.

I prefer to mount a light at bar height, this is enough to see how deep are ruts and potholes, and to angle the light enough downward so as not to blind riders and vehicles on coming up the from the opposite way.