For me it would be my Browning A-5 Sweet 16. The best part is that I still have it. It is just like the one my dad used to have. He found it used and gave it to me as a christmas present, along with an extra barrel. Then he gave his to my brother. My dumba$$ little brother. Oh well, at least I got two barrels.
The other gun I just love to shoot is my Ruger Super Single-Six. Classic styling, cheap ammo, and pretty darn accurate. Its the one I will use to teach my boy to shoot a pistol with. And then one day I can pass my Browning on to him.