It is common to use halber to indicate a cause, a reason or an end for something.
Der Einfachheit halber hier ein einfacher Beispielsatz.
Now 'Einfachheit' is feminine, so 'halber' is absolutely correct. For a masculine noun it would be:
Des Friedens halben hier ein freundlicher Beispielsatz.
I feel very uncomfortable writing that. And I'd never use it in a conversation and I really only once heard it beeing used (and that was in a play from Goethe). Is it just uncommon or is it wrong to decline it? May masculine nouns be combined with 'halb'? Would it be (for some reason) more correct to not decline it and say:
Des Friedens halber ein freundlicher Beispielsatz.
I know that I can always circumvent using it by using more common phrases. Still I'd like to know if there is something wrong with the masculine case. And if so: what.