Tag seeking rifle
Give it a 2 fire modes.
Tagging mode: is tagging bullet. If you hit the enemy with that bullet it is tagged for say 10 seconds but makes no damage.
Tag seeking mode: is tag seeking bullet. If fired close enough to tagged guy bullet will curve and hit the guy. Damage is negotiable. I guess OHK if tag is on the head and 2HK to the body?
tag should also attract bullets form other TR snipers. One tag of all. Make snipers to work together as a team
The tagged soldier must have some indication that he was tagged by a sniper so that he could run away and hide or just be annoyed by that. To remove the tag instantly we could ask medic to heal that will also remove the tag.
We could even introduce tag seeking rifles for other classes. So, infiltrator tags the guy and other just use tag seeking bullets to kill it. Possibilities are endless
That will not be overpowered because you do no damage while tagging and can kill only from the second shot. But it could be fun.