Since you said "OFF-ROAD" and not "FOUR WHEELERS/4x4s" I will include some off-beat suggestions.
Tractors can get absolutely anywhere. Dual-wheeled rear tractors are unlikely to get stuck in anything, and can climb ridiculous grades.
If tractors aren't your type, and you don't care so much about speed, then go for a
Rokon motorcycle is two wheel drive, has a 15-16 inch ground clearance, tremendously huge low pressure tires that will allow flotation in water ( get off and float it across a stream, go figure ), and can climb ridiculous grades.
Here's a link.
http://www.rokon.com/products/trailbrkr.htm
Of course they only can go 20-40 mph in top gear, but they can get into places no jeeps/mercedes benzes/cars can. Oh yeah, it can tow 3,000 pounds too.
Of course, a 4x4 ATV with a winch is unlikely to get stuck anywhere, and hauls ass...