Nightmare, an original Magic horse, was a staple of core sets up until the 2017 Welcome Deck
Specifically, its mana value is always 3
Territorial Kavu legitimately is a frightening card in Modern, but that's mostly because the combination of fetch lands, shock lands, and Triomes consistently allows it to be a 5/5 on Turn 2
Usually, I take the cards in Izzet, but you can do it in other ways
2003 Crystal Charizard (Skyridge) The Crystal Charizard from Skyridge (Wizards of the Coasts final set) is exceptionally scarce, especially in Gem Mint condition
As with most of the TF games as well, if you are newcomer to the TF series, tag force 5 is a good game that will eat up a lot of your time