Improved Arrow Collisions

Arrows should react differently based on which blocks they encounter upon being fired. For example, arrows should shatter glass panes, have a chance of passing through iron bars, and bounce off and convert to item form upon hitting a hard block such as stone. I'm recommending this improvement because it would not only add a touch of realism to the game, but because it would add some interesting mechanics in the areas of PvP (being able to shoot other players through iron bars and windows), minigames (perhaps a game that uses glass panes as a different style of target), and building secure bases (there would then be a tactical advantage to using iron bars in your windows as opposed to glass panes).