The fact that Guardians can run in to other Guardians and bump them, or melee them is really annoying and frustrating. This problem is prevalent in the Crucible and it leads to teammates bumping other teammates out of cover to their deaths or making others miss shots. Also griefing Titans doing a running melee on their own teammate pushing them off a ledge, because they thought THEY should get the heavy ammo, even though my friend had it first. This problem is also prevalent in raids, for example the jumping puzzle in Crown of Sorrow, plenty of Guardians bump each other to their deaths. My solution is to allow Guardians to walk through other Guardians and no more bumping, ever.