Area chat/PVP zones: Two things that would seriously increase the greatness that is Destiny
There are actually a few areas that could use a little work, but these are 2 things I think would increase the game exponentially.
First- An area chat. This would allow you to automatically chat with people with the area you are in (about as big as a combat area). Not only would this make public events or even just random team ups more fun but would also increase the likelihood that players will join a fireteam with random players. Kind of like breaking the ice.
Second- PVP zones. Areas across the map that allow PVP. Could be random and usually be in areas where there are no other enemies with a chance it week generate where there week be other enemies. Could work something like public events, but there should always be at least one PVP zone open on a map.