Vayne's Night Hunter
I think that Vayne's passive, Night Hunter, should have a buff icon when it's active. Currently, the only way you know Night Hunter is working (besides noticing you're going a little faster) is to directly look at your movement speed. I realize this won't be much of a change, but I think it'll provide a little more clarity and understanding for new players. After all, it doesn't take a lot of work to add a buff icon, and there is no reason not to have it show up in the HUD.