Best gigglemaker is nuzzling her belly, hands down bar none, at least for me.
Daddy makes her giggle by holding her stomach down and swinging her in and out, especially towards me. Or holding her at his side and gently jerking her back and forth like an old style machine gun saying "cute cute cute cute!" He claims he's the adorable mafia.
Nibbling her toes and fingers always is good for a laugh, and she makes herself laugh by playing peekaboo or offering us her food and then pulling it back at the last second.