I have the older CMG Sonic, an EDC Arc AAA with a stashed spare, and a lug-body Peak 1AAA 1LED "snow" that I just got and reviewed in the reviews forum. Arcs now command ridiculous prices on the secondhand market, so I wouldn't bother unless you're a collector. The CMG is just not as nice a light as an Arc or Peak, but it's a lot cheaper (under $10US) and is arguably a better value. The lug-body Peak is just about an exact copy of the Arc, except a bit lower powered (that's objectively neither good nor bad, but everyone here seems obsessed with making the light as bright as possible, which is not really the point of these small lights). It's quite nice. There are indications of a lug-body 3-led Peak but it's not available on their web site as of right now.
If you just want a practical keychain light, I'd say skip the whole madness and get some of the Photon II clones that KevinL is selling in the BST forum. They're $1.25US each plus $2.50 shipping worldwide (he's in Singapore) for up to 6 pieces, so for the $30 or so that you spend on a Peak with shipping, you can get about 20 of Kevin's lights. Then you don't have to worry about finding batteries--just open another light when the old one starts getting feeble. Unless you use your keychain light an awful lot, they really do last quite a long time. And they are great gifts, cheap to hand out and always appreciated. They're about as bright as the Arc or Peak 1-led lights with shorter runtime, followed by a long tail of getting gradually dimmer.