If you've got a userscript manager installed, such as Tampermonkey, you can use this userscript:
// ==UserScript==
// @name Quick page title copier
// @namespace http://stackexchange.com/users/4337810/
// @version 1.0
// @description A userscript that lets you quickly copy the title of a webpage
// @author ᔕᖺᘎᕊ (http://stackexchange.com/users/4337810/)
// @match *://*
// @grant none
// ==/UserScript==
(function() {
document.addEventListener('keyup', function(e) {
if(e.ctrlKey && e.shiftKey && e.keyCode == 67) {
window.prompt('Press Ctrl+C', document.getElementsByTagName("title")[0].innerHTML);
}
}, false);
})();
It doesn't directly copy, like @Aswin's script, but it prompts you so you can just ctrl+c it.
Default shortcut is ctrl+shift+c