The Portal 2 Ping tool would help immensely in Destiny, especially with no voice chat. Each fireteam member should have a color, and be able to ping things like in Portal Co-op. Pingable things should be enemies, surfaces, chests and resources, etc. R3 doesn't do anything currently, so binding it to that would be dandy.

Oh man, I'd ping spam the terrible players on my team incessantly!