I carry a windmill in my daypack.  My psk contains a $7 mag flint among other fire starters and my keychain sports a 3" by 3/8" cut down magflint.  For lighting a candle or campstove, a lighter is the superior method.  For lighting a campfire, however, I'll choose magnesium, vaseline cotton and a good spark every time!
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Two is one, one is none.  That is why I carry three.