All of my Pokemon games are used; I don't have the money for a new copy. Though I might get a new copy of SoulSilver for my birthday; I was commenting on it to my mom and she liked the pokewalker feature. Sees it as something to finally get me off my behind and move around.
When I got Diamond the first thing I did was reset it... Even if it'd had good rare pokemon in the PCs from the previous owner I had nothing to transfer them to. Eventually I figured out that getting the GBA games would bring in more pokemon, so I set out to look for them.
Total and utter noob that I am, I bought a cheap used copy of LeafGreen off ebay. Turned out to be a fake copy. It played fine, no glitches or hangups, but the Leafgreen insert pokemon never appeared in diamond, nor was there even an option to migrate them. I was not happy; I'd gotten a couple nice Vulpix in leafgreen. That fake copy is now gathering dust in my sock drawer.
After some sulking and growling, I managed to locate an authentic copy of LeafGreen and snapped it up. The previous owner had only four gym badges and nothing fancy in the PC, so I went and caught a couple common pokemon I needed for my pokedex, caught and transferred over zapdos, and transferred over their starter (wartortle). The game will now be reset and I'll play through it on my own.
I also got my hands on a used, authentic copy of Emerald. No hacks or anything as far as I can tell. The previous owner had eight badges but had not faced the elite four yet. I used their save file to catch a couple common pokemon and the three Regis, then transferred them and the starter (blaziken) to Diamond so I could wake Regigigas. Now I will reset that game and start over, too.
A friend of mine down the States has spare, legit copies of Ruby, Sapphire, and FireRed. She's going to send them to me as soon as she gets the chance ^_^
After some poking around the used game store I found a used copy of Platinum. It needs to be blown on before being inserted into the game slot, but it works. The previous owner had separate boxes for different-leveled pokemon. Nothing too fancy in the PC, and no shinies. They had caught the lake legendaries I'd accidentally knocked out in Diamond, so I transferred them over, caught magmar and electabuzz, then put it aside to restart and play through later.
My sister had a copy of Pearl, also used, but she'd restarted it to play and ended up not liking it. She gave it to me and loaned me her DS so I could trade evolve the pokemon I have that require trading to evolve, and then I restarted it to get the starters. She'd gotten lost in Wayward Cave before giving up, so I had to restart the game just to get out of there. Right now I'm playing through it to get the Pearl-version exclusives for my pokedex in Diamond.
On the subject of shinies, I only have one. I was hunting for Shuckle when I had a Random Encounter with a shiny Floatzel. I suck at chaining, apparently; I never get above 17 in the chain before it breaks >.<