Indicator of who is talking right now. Some people just talk rubbish, or are very laud, or annoying. Very often I wish to mute one annoying person, but I can't because often I have no idea who is talking right now. I wish there was a simple "speaker" icon that would show up whenever someone talks. It could show up when the certain volume threshold is reached, to show someone speaking. That would allow me to quickly mute all the unwanted noise.

Also a volume slider for voice chat would be great.