I am going to start adding those who gank my lowbies more than once and periodically go make their life miserable for a while using #4 option.

If I am questing I will usually just kill an ally who gets in my way or just gets too close to me. If they back off I leave them alone. Often simply right clicking on them to show an aggro alert is enough to get them to back up a bit.

Those that caused me serious problems (ie, 10 boxing with 5 80s trying to level my lowbies) over and over? Going to double team them in the future. One group kills him while one group waits at the grave site.