TCAS, even though rarely used IRL, is quite handy when flying on VATSIM, especially in uncontrolled airspaces. Same goes for hold function and even offset, which is a cool little trick to use when flying online with friends. Even though rarely used, in a flight sim they can be really handy! Just pitching in so you see what is important to the customers If I had a say, I'd have these functions before any of the other items!