[EDIT]
Yeah, yeah, yeah! Ignoring is all fine and well, it's so GROWN UP and old-school, but to be honest, it doesn't work that well. Don't fool yourself!
[/EDIT]
Well here is what I do or would do:
[hr]
Start yelling at something (not someone). It helps.
[hr]1.) Get a punching bag
2.) Print out the avatar of mentioned idiot who offended you
3.) Adhesive tape
4.) ???
5.) Punch, Kick, rinse and repeat
6.) Profit
[hr]
Follow his/her latest post and see him/her verbally brutalized and raped by another forum member and sit back and enjoy. If you like compliment the other member.
[hr]
Lure him to insult you even more so that he breaks the rules and then report him to the nearest MOD.
[hr]
Deliberately overreact even more. Simulate your own mental instabilty and go ballistic or completely wrist cutting emo depressive, if he/she apologize fine (feeling bad, huh?) if he/she humiliates you further you can either say you just made that all up and in fact you know what a sad little lonely pr*ck/p*ssy he/she really is.
[hr]
How dare you discuss your Grandmother's recipe for chocolate cake???
I HAVE YOUR EATEN BY YOUR FOR PROFIT SINCE YOU ARE IN TO SUCH THINGS. RARRRH...
Use comedy/irony/sarcasm/cynsim all together (if you are good at it) against him/her. If the other users start laughing at him/her because of you everything will be fine.