Versatile move. The Flip can act as a suprise move, a combo tool and even as an anti-air of sorts.
The Weak version is fast (and has really fast recovery) but has little range, while the Strong version takes a while to come out but has more range.
You're able to go either forward (with QCF+K) or backward (with QCB+K). Follow-up options are as follows;
-hold Back = Backward Dash. He performs his backdash upon landing.
-hold Up = Super Jump. He performs a Super Jump upon landing.
-hold any P = Dashing Elbow. He performs a straight dashing elbow, hits mid.
-hold Back, then SP = Extended Backdash Elbow. He does the backdash flip and then the dashing elbow. However this elbow cannot be Special/Super cancelled.
-hold any K = Wolverine Sweep - Identical to his crouching Strong Kick, although he now has three different ranges available.
The Wolverine Flip has gained EX versions as well. QCF+2K results in a Flip followed immediately with a launching double swoop kick.
QCB+2K results in a quick flip backwards followed by a downwards diagonal Ki Blast fired while automatically quickly jumping backwards.
For both these EX versions, you can still make the same follow-ups come out by holding the corresponding command, except with the EX Forward WF if it hits.