Important,yes. Iconic, no. Arguably the last iconic X-Man introduced was Rogue. One could argue Gambit though due to his inclusion in TAS (which would also cover Jubilee since she came before him) and Psylocke who, even though wasn't but a bit player in one story in TAS, has certainly became a standard inclusion in X-history. But I'm going to stick with Rogue.
To me iconic would be Cyclops, Jean, Storm, Wolverine, Beast, Rogue, Nightcrawler, Kitty and Colossus. Maybe Angel and Iceman if we stretch it.