Not entering into any logo competition here, but it might be interesting to do something completely different (although I vaguely recall some other altcoin doing this, I can't find it now);


Heavycoin(ium).  Looks like a periodic table element, rather than the ubiquitous round 'coin'.  The element (proton count 126) is actually Unbihexium, which is a superheavy element, suspected to be in the island of stability.  Its rumored most stable form would be doubly-magic, but for the mass I instead chose the first element of the initial hash values, in decimal expression (with a decimal point thrown in for no good reason other than artistic license).  Abstracts pretty well into small icon form (drop everything but the 'Hv').  On the down side, Photoshop and the show Breaking Bad have made using that form somewhat cliché.