How do I cut an oreo?
Try freezing the oreos first and then cut with a sharp knife.  Let the oreos warm to room temperature again.  They will not lose any texture or crispiness.

Update:

In the name of science, I froze some oreos and tested the outcome.  Freezing the oreos made the cutting much more...achievable.  A room temperature oreo just wants to crumble in too many places, but a frozen one holds together better.