I consider AA too large for my keychain, I prefer AAA lights with 3 modes, and a place for a small split ring on the tail.
here is one with a magnet on the tail, and with the option for a Nichia.
I always prefer Nichia LED.
the 10180 lights are a nice size for a keychain imo, but I do not consider them a serious task light, more like a keyhole finder. They have two modes, 5 lumens, and 100 lumens that kills the battery in less than 10 minutes. The 3 mode AA lights do aproximately the same outputs, plus a middle mode of about 20 lumens, that I find most practical.
I dislike a magnet built into a light, I prefer to place a magnet where I want to attach the light. (Eneloops stick to magnets, through the light body)
I agree on lobster over magnet for necklace
I like magnets but I put them on other objects (fridge, car, server rack…), not in my pockets
pics are links to more pics
note the pocket clip oriented to clip to a hat brim, optional but also serves as an antiroll device when the light is off my keys. Also note the lobster is on the keys, so there is nothing but a small split ring on the light. I often hold a light in my mouth.
for a USB charger, Im a fan of the Olight Universal Charger, not built into the light, so I can keep using the light while charging.
pic is a link to more info about the charger
very small, very lightweight
the black light, pic is a link
only one mode, about 100 lumen, nicely spread beam, no hotspot, which is useful for close range. Prolonged use eats up the battery in about 30 minutes, which is why I like the 3 mode lights, on medium (about 4 hours)… more time between changes
here is an AAA JetU
as an example of what I would not buy again, I do not like that it has Last Mode Memory:
