Like I said in a bunch of other topics, normal cards obtainable in packs, have no rarity to me, nothing is more rare then another in boosters. Well, EXs are same rarity as other EXs, and so on. I buy cards by the boxes, since I play at major tournaments like TormentedSoul did at his States. (Except I never win them XD)
So, my card would have to be my autographed Legendary Collection Gyarados, autographed by the artist of the card himself, Kanji and all. It was given to my friend whom I go to the tournaments with, so it has sentimental value, since it was given by her. Also, my Bilengual Eggecutor is fun to look at, given to me by her and her dad as well. Along with my Japanese Shining Mew, given to me by you know who by now. XD
So yeah..the cards that mean a lot to me are the cards given to me by my friends, and are harder to obtain, especially the signed Gyarados. ^^