The voice chat system.

[Roh_]

It's actually a good idea. And some of the commands could have a use if you could get the lemmings in pub to listen. But there are a few more that could be far more useful. Such as "Behind you!". The noise coupled with the fact that your team echo popping up for save a lot of people. I've tried using the whistle... but they just ignore it.

[Thomas Dixon]

Even more important ...........   Flag and gate

[Roh_]

That's only if you play siege. Here is one that useful in any mode "Stop you fucking Lemmings!". For when your team can't find two brain cells to rub together and just charges forward at the worst possible time.

(Yes I know there is "Hold your ground" but I would like it to be more insulting as the dumbasses who play this game still charge toward fail as fast as possible.)