Copy from Excel without Line Break

Ctrl+C > Ctrl+V > Backspace is probably better than the accepted answer due to fewer key strokes. I know this doesn't really answer the question, it sounds like your question is really a feature request. As mentioned in the comments here is a macro solution as well:

https://stackoverflow.com/q/14695836/145173

Sounds like too much work to me to avoid a backspace key stroke. If it's large grabs and pulls, I would just suggest using Notepad++'s advanced find/replace and exploit the \n\r\t characters that are the real text appended to the copy/paste and replace them with nothing.

Simply press F2 to edit the cell, select all text (Shift+Home ought to do it, or Ctrl+Shift+Home for multi-line cell), then copy (Ctrl+C) and paste (Ctrl+V) without line breaks being added.