It means to shove a cactus up your ass or cunt or whatever the fuck you have they're telling you to the nearest cactus and then fuck it
1.Somebody's being extremely obnoxious go fuck yourself with a cactus
2. Someone wants try playing a very cancergame like that stupid cat Pictionary you say how about we play this game it's called go fuck yourself with a cactus the rules are simple go fuck yourself with a cactus
3. Somebody asks you how would you like to do something very stupid You say how would you like to go fuck yourself of a cactus
(Phrase) Used to express extreme disbelief. Usually used after witnessing something exceedingly stupid, or being tasked with something exceedingly difficult. Sometimes also used to express frustration.
Father: Son, can you take out the trash?
Son: No dad sorry I'm working on my KillStreak.
Father: NOW son!
Son: Well fuck ME in the ASS with a CACTUS!