Identifying the Icons on Bottom Center Screen

I'm aware of the icon that shows up when you're near a supply crate to indicate you're refilling ammo, but what are the other icons that sometimes show up?

There's one that is triangle shaped with a "heartbeat" line that I've seen (as best as I can tell) and possibly others that show up quickly that I miss.

I can't find a good summary online of what all the various icons are.