Old melting chocolate problem?
You might try melting it into some water.

When melting chocolate, a little bit of water will cause it to seize (break and become grainy), but if you use more water to start with it will melt smoothly - about a tablespoon per six ounces should work to start, add more till you've reached your desired consistency.  It has to do with the chocolate being soluble in either fat or in water, but having trouble in the middle when they were competing for sugar and cocoa solids.  If you do this, you are basically making a chocolate sauce - even if the proportions mean it is a fairly thick one.  Of course, after you have made it you can doctor it to your tastes, thin it till it is dippable, add flavors or additives, as you prefer.

Alternatively, you might melt it into something richer for your sauce - milk, or cream, or butter.

These alternatives will make your chocolate sauce progressively richer, depending on which one you pick, and may alter the flavors more than plain water (which may or may not be desirable to you).  They do also have water in them (in decreasing proportion), but in an emulsion with fats which means they are less likely to cause the chocolate to seize.  You might start with the same proportions, one tablespoon to six ounces, and keep adding until it has reached your desired consistency.

Of course, you can use other liquids (like alcohol) or fats (like oils) to thin the chocolate and make the sauce, but they will be increasingly less like the chocolate you started with the more flavors you add, and more like a fancy chocolate sauce.  Which can be nice, but may not be what you're asking for.