To be honest I’ve tried so many over the years and mostly given up. For web based stuff I can recommend UXPin, it’s the best I’ve found. Apart from that and particularly for games there’s NOTHING like paper and pen. Page after page, drawing after drawing. I have a book that is about 1.5 inches thick of nothing but years of game design drawings and ideas. I love flipping back through it from time to time and get a buzz out of the old ideas.