In the $40 something to approaching $60 range, the Cygolite Metro series is worth considering. (I've seen those prices $5 to $10 lower in recent months than the $47 and $59 prices I see today.)

Things to like:

• the "DayLightning" mode is very noticeable in daylight
• the "SteadyPulse" mode is useful in the evening
• one piece / no external battery required
• 110 grams / moderate size and weight
• sturdy handlebar mount
• USB rechargeable
• build quality appears fine