Update: A Tyrantrun EX dragon card. Now we need the a Tyrunt dragon card, a regular Tyrantrum wouldn't be bad either. It's a good counterpoint to our other alternates; The trainer kit will give us psychic Latios and Latias. Roaring Skies will give us colorless Skarmory, colorless Shaymin, fairy Togekiss line cards, Dragon Reshiram, and Dragon Zekrom as well as amazingly giving us both types for M. Rayquaza. One of the three pack blisters will FINALLY give us the fighting Pangoro that I think we should have gotten in Furious Fists.
Rivershock mentioned some cards are made 'typed' by their weakness. That is in fact true in some cases but not all:
Venusaur line was made 'poison' in Crystal Guardians by being psychic weak, with FRLG Venusaur EX also being 'poison' but no regular Venusaur..
Charizard was only made 'flying' in FRLG with it's EX being electric weakness but it's still just like base set Charizard, it seems more like an afterthought.
Butterfree has a few 'flying' ones through electric weakness.
Beedrill line though has never been psychic weak, always fire. That comes across as always bug, never poison type.
Crobat line has a few 'flying' by virtue of electric weakness.
Vileplume line has a few 'poison' typing by weakness. Of course as noted there were already purple bordered Oddish and Gloom anyway, making this one an oddity no matter how you want to slice it as far as I am concerned.
Venomoth line has never been psychic weak either, making it always bug and never poison.
Bellsprout had one psychic weak card in Aquapolis but Weepinbell and Victreebel have never been given psychic weakness so no poison typing.
Gyarados is interesting. It has some electric weak cards, but some are weak to grass. This has to be card mechanics because Gyarados is not weak to grass types like most water types are.
Ledyba has an electric weak card for 'flying', but Ledian does not.
Ariados has had a few 'poison' cards by psychic weakness.
Xatu line has a few electric weak cards for flying.
Jumpluff line is always weak to fire, never electric or water (ice) and has in fact been resistant to the type because of water itself. This makes it all fire and no flying.
Steelix has no 'ground' type even by weakness.
Qwilfish has no 'poison' type even be weakness. Like Gyarados it is weak to grass, I assume by game mechanic, even though poison typing prevents that in game.
Tyranitar has two EX's that are weak to grass which could also represent 'rock', much like Dark Tyranitar technically does.
Beautifly and Masquerain have a few lighting weak cards for 'flying' representation.
Still of course missing Ralts and Kirlia as fairy types, along with a regular Gardevoir.
Ninjask has a few lighting weak cards for 'flying' representation but every Nincada has no ground representation by weakness.
Aggron line has no ground representation even with just weakness, Team Magma variations not withstanding.
Camerupt line has no 'rock' representation and I can't count weakness here because both types are water weak.
Cradily EX is weak to water so this could be 'rock' representation but Lileep does not have this.
Tropius has a few electric weak cards for 'flying' though if Skarmory can be colorless I think Tropius should too.
Bastiodon has no cards that are water weak to represent 'rock'.
Mothim has no electric weak card to represent 'flying'.
Combee has an electric weak card to represent 'flying' but the only Vespequin to be electric weak is the SP version.
Drifblim line has no electric weak cards to represent 'flying'.
Yanmega has no electric weak card to represent 'flying' though Yanma does.
Gliscor has no card to represent 'flying' though since it can't be electric weak and water is approximated to ice there might not be another alternative without making it colorless.
Swoobat line does have electric weak cards to represent 'flying' as does Sigilyph.
Fletchinder/Talonflame will have water weak cards in Roaring Skies, all lines previously have been electric weak instead, this could serve as a 'distinction' between fire and flying.
Hawlucha is already electric weak to represent 'flying'.
The neat thing about this though is that at least certain things get representation this way that otherwise wouldn't happen. My prime thoughts here are the water/ice types like Lapras, Cloyster, Dewgong, and the Walrein line who each have one form of ice represented and one form of water represented. The only line for this for Walrein is in Power Keepers, with Walrein itself being an EX.
With Roaring Skies giving us some stuff that work specifically with colorless types, I think it would be nice to see cards like Tropius and Hawlucha follow in the same vein as the new Skarmory. For some reason I just really want to see the Aegislash line in purple border and definently want to see the Venusaur line purple bordered. I'd also like to see some of these 'halfies' get closed up, in other words we get a grass Phantump and dragon Tyrunt to follow up their 'evolved' forms getting their alternate types. I am hoping the Emboar EX in the Togetic EX vs. Emboar EX thing is a fighting type Pokémon, and being backed up a fighting type line of Emboar/Pignite would be great as well. And of course still pining for psychic Delphox and fighting Chestnaught.
What other ones would be great to see?