There are a number of apps floating around that can strip rich text formatting from whatever you’ve copied to the pasteboard. I’m not sure why you’d need to buy an app for this. Here are two ways to get plain text.
⌘⌥⇧V – Paste and match style will give you plain text if you’re pasting into plain text. Otherwise you’ll get rich text that matches the formatting applied to wherever you’re pasting the text. I use this one a tonne in spreadsheets where I’m collecting information from web pages.
pbpaste | pbcopy – run this at the command prompt. It just pipes the pasteboard contents back into the pasteboard, but will remove all formatting as a result.