The craziest gun trade I ever made was when I was exhibiting at the big Ft.Worth gun show at Will Rogers in 1983. A guy kept going by my table admiring my shotgun collection(U.S. military marked riot and trench guns). Concurrently, my gun show buddy's had a table right next to me. They were really into militaria and edged weapons of WWII, mostly German items, but a few from other countries.
The guy walked by for the 4th or 5th time & I finally asked him, what he was going to buy. He picked up 3 or 4 shotguns, and settled on a Remington M31 riot gun. All proper markings...arsenal rework, proper cartouche on the buttstock, etc. He said he didn't have enough to buy it out right, and I said "what do you have to trade"? Not much he said...only a wrist watch. I said lemme see it. It was an Omega Speedmaster Professional, first variant(wind up kind, pure mechanical movement...the original moon watch). I gulped and offered the M31, he laughed. I added 2 cloth survival maps(1 from WWII, 1 from cold war), he said no, and went on down the line. 2 hours later he came back to barter with me. He said he liked the Webley No.2 Mark 1* on my buddy's table. I turned to my buddy and said "trade that piece of junk Webley for my Mauser Commercial HSc that has a broken firing pin??? (He'd been eyeing it for more than a year). "Nice gun, but broken firing pin". I said how about the HSc + $20 to boot? "Make it $25 and you have a deal." DONE!" Traded my HSc(wartime production commercial German pistol relatively rare) for the Webley. Handed the passerby the shotgun, the Webley(complete with original holster), the 2 cloth maps, and threw in a U.S. Navy PAL RH 36 fighting knife of WWII. It was in mint condition and hated to see it go.
The guy took off the watch and handed it to me. He said he didn't like the watch anyway. Sooooo it was a win-win trade for both of us.....but I think I got the better end of the deal.
[the Rem. M31 riot gun was 1 of 2 I bought for $137 each 3 years before, in Good to V.G. condition, but all original. The maps? Worth about $45 for both of them back them. The Webley...about $125 back then. The knife....about $40.]
My worst trade? 2 years before I traded a CZ-27(.32 acp) Nazi wartime production, all Nazi markings, for the Mauser HSc that had a broken firing pin!

I really wanted the HSc, and I wondered why the guy would want a CZ-27 in trade for the HSc on an even trade. I found out.

But it all worked itself out quite well.
BTW, the watch I traded for? Worth today(used) about $2,299.99 according to amazon.com:
http://www.amazon.com/Omega-Speedmaster ... B000EJPDOK" onclick="window.open(this.href);return false;