...Personally my most prized card is an English Happy Birthday Pikachu. It's not particularly rare. But I won it through the WotC giveaway where only 100 (I think... It's been awhile ago) were given out. Unfortunately there's nothing about the card that sets it apart from all the other Birthday Pikachus. Yet I prize it personally as much as many would prize the No. 1 Trainer card or Prerelease Raichu. That doesn't mean that I could go to eBay and sell the Happy Birthday Pikachu for thousands of dollars. It just means that I find a lot of personal value in that card. I think that's what Nicholas3652 was saying...
The following cards are some of the rarest, most expensive, prized and historical cards in the world.
1998 Pikachu Illustrator
1997 Pikachu #1, #2, #3
1998 Pikachu (Lizardon) #1, #2, #3
1998 Pikachu (Kamex) #1, #2, #3
1999 TMB #1, #2, #3
1999 SSB #1, #2, #3
1999 SNAP Best Photo Contest
1998 Kamex White 'R'
1998 Parent/Child Kangaskhan
1998 University Magikarp
1999 Tropical Wind
1999 TMB Articuno, Moltres, Zapdos
1999 Pre-Release Raichu
2000 9th Lucky Stadium
2001 Neo #1, #2, #3
2002 Battle Roads #1, #2, #3
2002 Battle Roads Elite Four Trainer
2004-present World Championship #1, #2, #3 (English)
2005 Champion's League
2005 Championship Arena
2010 Master's Key
To me it's a Blaine's Charizard signed by Ken Sugimori himself. I even got it framed
I got it when I was like 10 years old in a STS. He was there signing cards and I was the last person they allowed in line. I still have a picture of it.
To me it's my square cut Japanese Misty trainer (pics below). Knowing the Japanese quality control for cards, I still have no idea how it got out of the factory. Though sadly it has a few dings on the corners.
http://i10.photobucket.com/albums/a140/6969691/02132010261.jpg
http://i10.photobucket.com/albums/a140/6969691/02132010262.jpg
The illustrator has appeared for (public) sale four or five times in 15 years. That is hardly once a year. Second, the illustrator goes for more money. The one or two sales of the Pre-chu that we know of sold around the 10-11k mark. The illustrator edges that out a bit with the most recent sale ending around 12-13k....not to mention it holds the highest realized price of any card at 20k. Based off of the price the illustrator commands and its popularity and desirability I would have to say it takes the over all "most prized Pokémon card" with the pre-chu in a very close second.
It´s a very rare misprint, this is the only one I´ve ever seen.