Temporal value node? When I'm trying to make an animated texture or whatnot for a material, I often have to set a couple of keyframes on a value, make sure things are properly selected, then go back to the graph editor, set them to linear extrapolation, so on and so forth. This is rather cumbersome.
Is there a node—either built in or in an addon—that can replicate this functionality by default? It would save a lot of time.
Driver expression: #frame
You can use drivers with #frame expression.
It's basically feeding the field with the value of the curret frame. By using a multiplying factor you can set the pendency of the curve.

It's also easy to edit: just right click the field or type in to override the expression.