The Pokémon Trading Card Game has been around since 1996. Despite being over twenty years old, the game is still going strong to this day. Throughout the years, the Pokémon TCG has introduced many mechanics and features. Some of these include "EX Pokémon," which have been in and out of the game for years.
However, some of these other card types don't get the same treatment. The TCG has had many gimmicks come in for a set or two before they completely vanished from any future ones. The Pokémon TCG adds new mechanics and card types all the time, but these gimmicks never got a chance back in the limelight.
10 Prime Pokémon
Pokémon Prime were introduced in the "HeartGold & SoulSilver" Set, appearing in "Unleashed," "Undaunted," and "Triumphant" before being discontinued. After the TCG moved on from the "HeartGold & SoulSilver" series, it too would move on from Pokémon Prime, with their last appearance being in 2010. Pokémon Prime are an alternative form of a Pokémon, classified by its close-up art. The borders and names also tend to be holographic as well, making them easy to identify. Pokémon Prime are much more powerful than the usual Pokémon, with fantastic attacks and/or abilities.
9 Crystal Pokémon
A part of the "e-Series" of cards, Crystal Pokémon have never made an appearance since 2003. They only appeared in the "Aquapolis" and "Skyridge" Sets. Cyrstal Pokémon are all Colorless and possess the Poké-Body "Crystal Type."
This ability will cause the Pokémon to change into the Type of whatever Energy is attached to it for that turn, with a choice of three different ones. All Crystal Pokémon had attacks that used three different kinds of Energy costs. They would gain an homage in the way of Shining Pokémon, but were severely altered overall and never returned.
8 LV.X
LV.X were the main "Boss Pokémon" during the Generation IV era. They were introduced in the "Diamond & Pearl" Set, all the way until "Arceus" before the game transitioned into the "HeartGold & SoulSilver" Era. LV.X would have their last appearance in 2009. Unlike other powerful Pokémon cards such as EX, LV.X does not come with any drawback for using them. LV.X can not be used as an Evolution, meaning it has to be placed on a specific card that's already fully Evolved. LV.X can even use all the attacks and abilities of its previous form.
7 Pokémon LEGEND
Pokémon LEGEND was a very short-lived gimmick that started in the "HeartGold & SoulSilver" Set, with their last appearance being in "Triumphant" in 2010. There were only nine Pokémon LEGEND cards ever released, more often than not a duo of two Legendary Pokémon. Pokémon LEGEND cards were split in half and required both halves to be in your Hand in order to play them. The art took up most of the card, with the design of attacks and Energy costs in a unique pattern. They count as one card on the field, but separate cards in the Deck.
6 Owner's Pokémon
Owner's Pokémon were special Pokémon that were owned by Gym Leaders (and sometimes the criminal organization teams). They were introduced in "Gym Heroes" back in 1998, and Gym Leader Pokémon's only other appearance was in "Gym Challenge" in 1999. "Rocket" Pokémon would appear much later in "EX Team Rocket Returns."
The last we've seen of them were the Team Aqua/Magma Pokémon in "Double Crisis." Owner's Pokémon didn't change anything to the gameplay, nor alter the power level of any Pokémon. It was a purely cosmetic gimmick and one that hasn't been seen since 2015.
5 Pokémon BREAK
One of the most interestingly designed gimmicks, Pokémon BREAK cards have not seen any love since their last appearance in "Evolutions" back in 2016. They had their first showing in the "BREAKthrough" Set in 2015, the gimmick only lasting a year before being discontinued. Pokémon BREAK act as an Evolution card to be put on the final stage of the Pokémon. They keep the abilities and moves of the previous form while gaining an additional attack or ability with an HP boost. These went on the card sideways, covering the art. The art itself features golden CGI versions of the Pokémon, offering plenty of interesting designs.
4 Pokémon Star
Pokémon Star are Shiny Pokémon and incredibly rare. All Pokémon Stars are Basic Pokémon, and only one of any Pokémon Star can be played in a Deck. They were introduced to the game in "EX Team Rocket Returns" and retired at the end of the "EX" Set era in "Power Keepers." They last appeared in 2007, and have yet to have any sort of return or re-imagining of them. Many Pokémon Star cards were of Legendary Pokémon, along with some fully Evolved Pokémon and even a few Stater Pokémon. They were an interesting gimmick, albeit not the most powerful.
3 Dark Pokémon
Before the Dark Type even existed, the TCG had Dark Pokémon first. They were introduced in the "Team Rocket" Set in 1997, with their last appearance being in "EX Team Rocket Returns" in 2004. Dark Pokémon were "evil" counterparts to other Pokémon, meant to represent Pokémon owned by Team Rocket.
Later on, the Dark Typing would be given to Dark Pokémon as a Dual-Type in the "EX Team Rocket Returns" Set. Gameplay-wise they were no different than normal Pokémon, and have become a forgotten gimmick to both the player base and the card designers alike.
2 Delta Species
One of the coolest gimmicks the TCG, Delta Species were introduced in "EX Delta Species" in 2005 and discontinued after the 2006 Set "EX Dragon Frontiers." Delta Species Pokémon change the Type of a Pokémon, such as making Golduck an Electric Type instead of a Water. Strangely enough, despite the Typing change, they keep their original weakness, meaning that Delta Species Golduck would still be weak to Lightning. They were also one of the few gimmicks that came with lore, with the story of Delta Species being that they were Pokémon exposed to electromagnetic waves from scientists trying to find Mew.
1 Light Pokémon
The counterpart to Dark Pokémon, Light Pokémon first appeared in "Neo Destiny." Light Pokémon are also the most forgotten gimmick as that was the only Set they ever appeared in. Light Pokémon have moves and abilities that more often than not act as support, rather than having offensive traits as they generally heal or assist. Light Pokémon tend to have higher HP as well. Light Pokémon never had a Typing to become, unlike their Dark counterparts. Only twenty Light Pokémon were ever released and after twenty years of no new Light Pokémon, it's unlikely we'll ever see them again.