I actually have duplicate copies of Double Dragon 1 & III up for sale on Ebay at the moment. Awesome games that bring back great memories, even if the NES versions are gimped arcade ports.
Lately I have been picking up games here and there. My local Salvation Army has been getting a lot of good stuff lately. Lots of NES and Genesis, to go along with the plethora of crap PS3/X360 sports titles they always have in stock. Then as usual I also grab the odd good deal off Ebay, usually has to be at least $4 lower than current market value. Recent pickups:
NES: Gun.Smoke, Tetris 2, Ninja Gaiden 1, Jackal, TMNT II, Kid Icarus, 1942, 1943, Guardian Legend, Kung Fu
SNES: Alien 3
N64: Star Soldier: Vanishing Earth, Space Invaders
Genesis: Thunder Force III
PS2: Contra Shattered Soldier
BUT, just this weekend I went to reclaim whatever I left in my parents house when I moved and hit the jackpot:
My old Sega stuff! (and a few lost SNES games) I thought I had lost all this when I moved out back in 2003 but apparently I just forgot to take the box LOL. Now I'm tempted to by Sega Saturn games but they are god damn expensive.