Strange medical system was the first thing that struck me.
Or more correctly, the bullets that first struck me were strange, as they couldn't kill me.
And I couldn't kill friendlies. Not even deliberately

And then we spent ages kitting out for a submarine mission, flippered our way to the boat target, only for it to give us a 'mission complete' without any action.
Just a suggestion, and perhaps it already happens - but can we give new missions a bit more private testing before putting them up on public?