0 because it symbolises not

2 because it resonates with what comes after knowledge, i.e., wisdom

7 because it's, as we say at church, a Godly number

8 because, depending on one's willful deeds, you either build or destroy

17 because it reminds me of the out-of-africa hypothesis and/or the super-evolved children of perdition

20 because some "faiths" consider it a symbol of putting your best foot forward, i.e., being more Godly in one's ways of living

21 because that's when Sanusi Mutwa was born

psych! it's $149.98, because bitaxe's on sale on SoloSatoshi.com