Shooters on iOS that are still available?

There used to be a lot of shooters for iOS, like audio defense, nebula, sixth sense, and audio invaders. I believe all of these games are no longer available, and it's sad that all good things must come to in end. With that said, are there any more recent shooters that have come out which are enjoyable to play? I have scoured the app directories and found very little of note.