[quote=Derpestein]
I hate Meta-Gaming in Arena.Oh hey, my character has this strange, very specific weakness and your character knows it...SOMEHOW! Without it ever being shown IC! Cool!
[/quote]

That can go both ways. with people having "strange, specific. weaknesses" that make it literally impossible for the.other person to take advantage of. 

Same with weaknesses that are completely at the mercy of the.controlling player.