Valkyrie

The Valkyrie has been seen in official screenshots. It also appeared in GTA Online.

Rockstar has not shared more about the Valkyrie yet. This page grows as new trailers and screenshots come out.

More helicopters

Buzzard
Seen in the Extended Look. Earlier in GTA V.
Buzzard (police)
New to the series
Seen in the Ultimate Edition screenshots.
Buzzard Attack Chopper
Seen in the second trailer. Earlier in GTA V.
Maverick
Seen in official screenshots. Earlier in games including GTA Vice City Stories, GTA IV and GTA V.
Maverick civilian helicopter
New to the series
Seen in official screenshots.
Police Maverick
Seen in official screenshots. Earlier in games including GTA IV, GTA Chinatown Wars and GTA V.
Sea Sparrow
Seen in official artwork. Earlier in games including GTA San Andreas, GTA Vice City Stories and GTA Online.
DH-7 Iron Mule
Seen in the launch trailer. Earlier in GTA Online.
Eurocopter EC135-inspired police helicopter
New to the series
Seen in official artwork.
SuperVolito
Seen in official screenshots. Earlier in GTA Online.
Swift
Seen in the Extended Look. Earlier in GTA V.
Volatus
Seen in official screenshots. Earlier in GTA Online.