Well, online (unless u r host) it appears that you see NO bright red light at top of tower and there is NO charging sound, just the shooting laser thingy is shown which is a laggy disappointment for GDI as it slightly gives Nod an edge. Sometimes if its really laggy, u c and hear absolutely nothing and jus die

Oh, and same goes for those doggone voice-message icons. Offline or as a host, an icon will appear over someones head when they send a voice-message(ctrl and alt keys + numbers) online of course you dont c this due to latency, but it would help teamwork be somewhat less confusing

There are some other sounds that dont play online, but no others that are particularly important.