The following cards have become Legacy staples, but are not legal in Heritage. The list grows longer with every supplemental set release, thus further separating the Legacy and Heritage formats.
Use this link to Scryfall to see the full list of cards legal in Legacy that are not in Heritage.
White




As well as…
Recruiter of the Guard
Giver of Runes
Blue




As well as…
Force of Negation
Flusterstorm
Dress Down
Thought Monitor
Kappa Canoneer
Black




As well as…
Dauthi Voidwalker
Plague Engineer
Red


As well as…
Fury
Muxus, Goblin Grandee
Maddening Hex
Green


As well as…
Endurance
Force of Vigor
Gold




As well as…
Minsc & Boo, Timeless Heroes
Grist, the Hunger Tide
Baleful Strix ;(
Colorless






As well as…
Yavimaya, Cradle of Growth
Prismatic Vista