This performs a simple task (pretty) reliably: It puts all my tabs' URLs into my clipboard, separated by newlines. I use it with https://addons.mozilla.org/addon/multiple-paste-and-go-button/

To rate 5 stars, I'd like: to copy only the tabs I've selected, if I've selected more than 1; to copy the URLs of tabs which have been unloaded/paused for a while (instead they appear as "about:blank")