I am mighty.

[enemyofperfect]

Forget the brave little tailor; I can coax a fly out of the house without resorting to any violence whatsoever.  My skill, however, is matched by my generosity:  I will now, free of charge, disclose to you my remarkably efficacious methods -- and I can assure you that once you have gazed upon my instructions, you will agree that their efficacy is remarkable indeed.

The steps are as follows:

1. Get a bottle of water -- empty or full doesn't matter, but make sure the cap is screwed on tightly -- and place it on a flat surface in plain sight.
2. Wait for the fly to land on it.
3. Very carefully, grasp the part of the bottle farthest from the fly, and pick it up.
4. Proceed with extreme caution to the nearest door, avoiding loud noises, fellow humans, or excessive breathing.
5. If the door is locked, unlock it.  Open the door slowly and ease yourself, with bottle and fly, through it.  Take care not to alarm the fly with suddenly looming door frames!
6. With the door closed behind you, permit the fly to take flight and leave.
7. Return to the house, relocking the door if necessary, and celebrate your victory.

It is possible that there is a zeroth step, viz., allowing the fly to collide with your body as it buzzes about the room; I am skeptical of its necessity, but if the procedure outlined above fails to work for you, I would recommend performing it before trying again.

I have twice now achieved success in exactly this manner.