Most of the pickaxes in No Heroes Allowed can be unlocked by gaining Dragon Orbs in Story Mode, Dungeon-a-Day Mode, and Training Mode (though only one orb can be gained in this manner). There are 44 Dragon Orbs total. There are two "special" pickaxes, however, that can only be gained by going to the "Manage Save Data" menu under options. These two pickaxes require save files of "What Did I Do to Deserve This, My Lord!?" and "What Did I Do to Deserve This, My Lord!? 2" that are 100% complete.
The Pathfinder 6000 Pickaxe
Acquire 8 Dragon Orbs.
The Snacker Whacker Pickaxe
Acquire 19 Dragon Orbs.
The Sneaky Peeker Pickaxe
Select "The Power of One", and choose a WDIDTDTML1 save file that is 100% complete.