Luigi's Final Smash...Luigi's Final Smash...
Something to do with Boos? Luigi could summon King Boo to the stage and starting to vacuum it in. Other players could get sucked in too and at the end, the Poltergust would overheat and explode, sending caught players flying. Touching King Boo would also cause some minor damage. For the duration of the FS, Luigi's speed and jumping height would be slightly reduced, also preventing the use of any attacks. As a possible extra gimmick, players could hit King Boo to weaken him and thus end the Final Smash faster (but not too quickly).
Something to do with Boos? Luigi could summon King Boo to the stage and starting to vacuum it in. Other players could get sucked in too and at the end, the Poltergust would overheat and explode, sending caught players flying. Touching King Boo would also cause some minor damage. For the duration of the FS, Luigi's speed and jumping height would be slightly reduced, also preventing the use of any attacks. As a possible extra gimmick, players could hit King Boo to weaken him and thus end the Final Smash faster (but not too quickly).