I must say, I do love my Illumina Ti (Model CA1-Ti) from Titanium Innovations. It lives on my keychain and takes a regular AAA battery. It is extremely bright and seemingly reliable so far...

It was a gift...my dad found it on eBay I think...but it's product info can be found here...
It can be found here if you are curious

(The usual disclaimer for the above link...)
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"By failing to prepare, you are preparing to fail." - Frankin