This may sound odd, my front right wheel was in some water at an angle (going up my driveway). I gave it some gas and the car just sat there. The tire was obviously slipping in the water and the rest of the three wheels barely could move me up the driveway. Im sure there is some explaination, but I'd expect an AWD car to simply move the other three wheels if one had no traction.

 

i've seen this happen to my friends wrx
though he has 400 HP in his as well as crazy amounts of suspension stuff
it was tight looking, his drive way is at such an angle that when he goes up it (sideways) a 1/4 of his car is hanging off the edge