Due to the question being slightly unclear I will give two answers. The first answer is regarding the sword related to the Temple of Avo in the original Fable, this is Avo's Tear, You gain this sword if you take the good choice at the end of the game but only in The Lost Chapters. This does NOT appear in the stand-alone original game. You may also be thinking of The Sword in the Stone which is the Harbinger.
And my second answer regarding this weapon has to do with Fable II in the Temple of Light. If you donate a few thousand gold coins at midday then you will be given this weapon as a reward. It's called The Rising Sun.