Trapper is a non-canonical power-up that appears in Riesige Anlage and is exclusive in the Nazi Zombies game mode.
What it does:
The trapper power-up allows player to buy traps for one hundred points, so this is like a fire sale for traps. You can only turn on one trap as the power-up will disappear once used or over 20 seconds.
Why it is useful:
Well, I have noticed when that not many people use traps (my experience at the least). This may encourage people to use traps a little more. Maybe the reason you may not find people buying traps is because they are worth 1000 points and that seems a little much to a player.
What does it look like:
The trapper power-up has a green glow and has the same shiny metallic appearance as the other power-ups. The power-up itself looks much like a bear trap that a hunter would use.