The reverse holo of the English TV Reporter from EX Dragon is a very unassuming semi-rare card.
Also, if you ever come across a corrected-artist Japanese Ivy Pikachu, make sure to check if it’s glossy! Several members here have posted stories about their search (and eventual acquisition) of one. See here and here.
I think this is different than what the Sample cards are that you may be thinking of. The cards that actually have “Sample” written on the bottom right didn’t come from a pack (the one in that article is the packs that were given out with new Nintendo DS E-Readers). The stamped Sample cards were used in NYC to help demonstrate the new e-Reader technology.
These are also not the Sample cards, but closer (they share having a Japanese back and an English front) and fall much more into the “obscure cards” list.
Here is my Sample Gastly for reference:
Thanks man thats very enlightening as i have the pichu also. The zard tho is still unexplained 
il find out one day 
We also have this thread if you’re looking for cards with stories behind them, however you need to first read carefully to determine if some of them are actually available for collecting.
Are any L1 unlimited japanese cards still worth buying when they are found?
If you’re a collector who values rarity and unique items, L1 unlimited cards can be a fun and rewarding purchase, especially if you find them at a good price. However, if you’re looking for a quick flip or Instagram clout then they might not be the best choice.
“Waste no more time arguing if you should be a L1 unlimited collector. Be one.” - Marcus Aurelius.
Cheers!
Another one that just popped into my head:
2007, 2008, and 2009 Distributor Meeting Promos. A very polarizing history and release. Still a lot unknown about these apart from that they exist and there were supposedly only an handful made to give out at one private, annual meeting each year. The Munchlax is non-holo, and the Piplup & Turtwig are holo.
“It is not death that a man should fear, but rather he should fear never beginning to collect L1 unlimited” - Marcus Aurelius
“Furthermore I am of the opinion that unlimited cards must be collected”
-Cato the Elder
