[The Lucas]

Originally Posted by Adamskiy

P.S. - Another clever strategy I noticed was trying to throw ringers onto opponents robots when they were over on your side of the field, to cause them to get a penalty if they tried to pick another tube up. Ringers only got stuck on a robot like that once or twice, but it definitely helped.

Ringers intentionally put on opposing robots should not earn penalties for those robots. Ill go find the rule in a sec.

EDIT:

<G09> POSSESSION - ROBOTS may only have 1 (one) GAME PIECE in their POSSESSION at any time during the match. A 10-point penalty will be assessed for each infraction. Inadvertent bulldozing of GAME PIECES while the ROBOT moves around the field is allowed. Controlled "herding" of a single GAME PIECE lying on the floor is permitted as long as no other GAME PIECE is in the POSSESSION of the ROBOT. Herding of multiple GAME PIECES, or herding of a GAME PIECE on the floor while in POSSESSION of another GAME PIECE is not permitted (as this would be considered POSSESSION of more than one GAME PIECE). GAME PIECES may fall on to a ROBOT during the course of normal game play (e.g. a RINGER falls on a ROBOT while attempting to HANG it on a Spider Leg). In such cases, GAME PIECES that are already in the POSSESSION of the ROBOT may be played. However, the additional GAME PIECE must be removed from the ROBOT (either by the ROBOT or by an ALLIANCE partner) before it can POSSESS a new GAME PIECE. GAME PIECES may not be intentionally placed on opposing ROBOTS for the purpose of causing a violation of this rule. Any such GAME PIECE placements will not be considered in POSSESSION of the affected ROBOT, and will be ignored.

Emphasis mine. However, there is no rule against throwing ringers at an opponents gripper in an attempt to knock the tube out of it. I've seen that work.