A completely "style free" word processing software

For part of my job I have to copy and paste bits of info from lots of different sources into a single mega-document. I'd like to be able to work with a Word-like document that strips away all formatting and styles from from the source material when I paste it. "Remove source formatting" each time is very tedious.

I once had the Word settings configured to do this automatically, but ended up with something pretty buggy (for one thing, I could no longer paste into find/replace). But also, I'd like to be able to keep the formatting in the docs that aren't the mega-document.

So, is there a barebones caveman word processing type software? Even Plain Text which came with my Mac doesn't do this.