A weapon that kills only 1 person isn't exactly overkill nor is it ruin game play, It gives the T a useful way of preserving a dead body by setting a trap for anyone that walks into it. It gives the T an advantage but so does every other thing they can buy. Maybe we can add the detective weapon that allows them to pass the trip mine unharmed.
I agree with Kimchi on this one, we need to be careful what items donators can buy we do not want to become a pay to win community.