Karin
The Rebel is a Karin off-roader returning from earlier GTA games. Rockstar first showed it in an official screenshot (Grassrivers 02).
Image: Rockstar Games'67 Dominator Buggy
First shown: Rockstar media: Ultimate Edition
Bison (second generation)
The Bison (second generation) is a Bravado off-roader new to the series.
Blazer
The Blazer is a Nagasaki off-roader returning from earlier GTA games.
Caracara 4x4
The Caracara 4x4 is a Vapid off-roader returning from earlier GTA games.