More often than not forum posts have been successfully answered but the original poster never bothered to mark the answer that helped solve their problem as the solution. A post marked as solution is very useful for others looking for ways to address the same problem.

A lot of people in the community can identify the correct answer, but cannot do it unless they are the Original Poster (OP) or a Moderator.

The idea would be anyone other than the OP could mark a post on an Unsolved topic as a "Possible Solution", subject to be reviewed by a moderator. If validated by a moderator, after a certain threshold of time, and if the OP still hasn't marked any post as the Solution, this possible solution would become the definite Solution (and credited to the person that answered it).

In order to gameify this/make it more enticing for people to mark (potential) solutions, some small amount of points could be awarded to the person that initially marked the possible solution too.