I've been working on getting the IceTV parental rating and category/genre information to display on the Beyonwiz T/U series PVRs, and in my testing I've noticed that a small number of current shows don't have any category/genre information:
Full Proof
Gruen XI
Landline
Odd Squad
If I look back at some older IceTV EPG data dumps, there are some more, but they may have since been fixed:
Almost Naked Animals
Anger Management
Atoms Of Fire
Extraordinary People
Great Whites: Secrets Revealed
Harold Blair
Market Values
Medical Rookies
River Cottage
Saturday Landline
Ultimate Armored Car: The Presidential Beast
Wacky World Beaters