Actually, I believe the folks at the check-in desk are required by law to put the "Unloaded Firearms" tag INSIDE the suitcase/bag, so it is NOT visible from the outside, just for the reason you mentioned.
I usually put my handgun(s) in a small hard case inside the suitcase, both to prevent handling damage and to give the the luggage checkers something OTHER than the main bag to hang the tag on. It has worked every time I've flown with handguns (4-5 times pre-9/11, and 3 times post-9/11).
Don't forget to check the regulations on flying with ammo, too. If I recall correctly, some companies won't allow it in the same suitcase/bag as the weapon(s), and some will. Some require it to be in factory containers, others allow plastic boxes and other non-factory containers.
If you have magazine-fed weapons (rifles OR handguns), usually they won't allow loaded mags in the gun case; and at least once I was told I had to empty the mags that were loaded, even though they were in a different bag than the guns. Luckily, I had space in the ammo boxes for the removed rounds, or I would have had to give them up (loose ammo is a no-no).
If you have connecting flights, especially on the little puddle-jumper regional airlines, then find out if they have their own rules for guns/ammo.
Hope this was helpful.