I've used basic halogen bulbs, PIAA Xtreme white halogens, and these cheap Auxbeam LEDs, bro.

https://www.amazon.com/gp/aw/d/B01KFBPBC0?psc=1&ref=ppx_pop_mob_b_asin_title

I like the LEDs the best as long as you get the bulb mounted in the right direction in the housing. Not only are they bright enough at night but I also feel like oncoming traffic can see me better during the day.