Simple & reliable 18650 light under $25. Any suggestions?

If you like the C8 form factor and are ready to shell out $5 more, go for the XinTD C8:
http://intl-outdoor.com/xintd-c8-v4-xml2-u2t6-18650-flashlight-p-308.html
You can choose various tints (i have the XM-L2 T4 5B1) and drivers without disco modes.

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Local reviews:
Old model Review: XinTD C8 (SC-82)
Latest model Review: XinTD C8 SC-82/V4 (3C neutral white)