the engineering things the make or give your pets like the gnomish remote or the mind control helm. if you use this with your hunter or warlock with a pet out u will lose it. the mind control helm also can only be used in noncombat so a rouge would be perfect for that.

If your group is about to wipe a rouge can vanish and attempt to rez a rezer with the jumper cables.

Makeing guns and bullets in nice but is it worth giving up leatherworking or some other profession when u could buy them from another engineer?

Saping a goblin land mine sounds like fun :)