Had this happen to us last weekend:
2/10, A-40.
A11's legal forward pass is tipped by B99 at the A-36. The ball deflects upward and to the right. The ball is descending right above a group of opponents blocking each other at the A-37, when it 'boinks' off of A63's helmet, and deflects toward A77, who catches the ball at the A-38. Only slightly startled, A77 begins to advance, but is quickly swarmed by opponents and tackled to the ground at the A-39.
As R, I immediately signaled S11 when the ball was tipped by B99. Knowing it was touched by B, I knew the catch (touching) by originally ineligible A77 was legal. Next down.
Not terribly tricky, but unusual-to-rare.
My U noted that A77 would have been better off to just let the ball fall to the ground. Maybe. But what fun would that have been?