In the game, the only dark Chips that will appear in your fold are below, and next to them is the effect that they give you:

DarkCanon: Causes a buster bug that reduces stats to 1
DrkSword: Causes a movement bug that forces megaman to move forward
DarkBomb: Causes a movement bug that forces megaman to move backwards
DarkVulcn: Causes a movement bug that reverses megamans directonal controls
DrkLance:Causes a bug that removes five random chips from you folder from play
DrkSpred: Causes a bug that turns any panel megaman steps off of into poison panels
DrkStage: Causes a bug that gives you one less chip space on the custom menu
DrkRecov: Causes a bug that rapidly drains megaman's hp, even when choosing new chips

If the dark chips are used a lot, then megaman will automatically enter a battle in Evil form and be able to use the Dark Chips at any time.