Though it's not an NES find per se, my greatest find went like this;
I walk up to a garage sale and find nothing of interest. As is my practice, I ask if they have any old video games. The guy is, like, "I think I have a Genesis upstairs". Upon his return from the house he has a box, overflowing. I look in the box and see a bunch of stuff, but what really caught my eye was a Donkey Kong cart fo the intellivision. Knowing that I have exactly $3 in my wallet, I hope that he doesn't know what he has and plan to offer him $3 and sincere gratitude for the cart. He says, "I don't know how much this is all worth, but (turns to his wife) what do you think a buck?" she replies, "for the box?". He says, yes, and they agree. I proceed to almost have a heart attack, hand over my dollar and fight the urge to run to my car. Upon further inspection I discover that the box contents were:
       1 Donkey Kong cart for intellivision
       18 various (some rare) Atari 2600 carts
       1 Atari 2600 in mint condition
       1 Intellivision master component, 1st generation, still with the    
       protective plastic cover on top.
I lit some incense as an offering to the vintage game gods and played pitfall until I fell asleep. Long winded, but worth it.

Unicron78 wrote on 31. Jan 2008 at 16:30:


haha, that's awesome!  How much is that DK cart for Intellivision worth?

And nice DW3 find!  That's a downer to self-employment... no co-workers to harvest.

Sunday equals FleaMarket day in the Burgh and it payed off.  Wally Bear, Venice Beach, Pac-Man both grey and black Tengens: all were three dollars each.  However, the guy is out of games and won't be back.
                             
                                   

I  now have no private pond to swim at.

                                                                                                                             

No Really a nes find But I did get a UFO SUPER DRIVE PRO 6 for $50 at a pawn shop

I just got 3 famicom multicarts each with its own converter for $15 each  One even had burgertime

A new secondhand video game store opened just down from where I work last summer.  (Everything seemed to happen last summer...weird)  Anyway, I walked in and bought Contra Force, Lolo 2, Namco PacMan, and something else decent, I forget, for $40 

I can't ever find anything at Goodwill stores like I hear everyone on here.   I think there are too many ebayer's scanning the local stores

I bought a boxed copy of the crapfest that is Godzilla, but inside the manual was a perfectly preserved card for joining club nintendo with a picture of  mario from super mario 2. Was a nice surprise.