Default field values? This seems so simple, but after reading over the docs, I couldn't find an answer:

Is there a way to have a field have a default value in Craft?

In my case, I have a Lightswitch field that I want to be on by default, so my client doesn't have to turn it on every time they publish an asset.  But they still do need the ability to turn it off in exceptional cases.

I realize I could just reverse the logic of the field, but it raises a broader question of default field values (which would be useful to me).
As far as I know, the only fields that allow defaults are those that extend the BaseOptionsFieldType, namely Dropdown, Multiselect, Checkboxes, and RadioButtons. You could change your lightswitch to one of these other fieldtypes and have a default value available.