It is a useful command to help clean up unused class-maps:
RP/0/RSP0/CPU0:A9K-BNG#show class-map list type qos
Thu Sep 12 14:58:56.383 EDT
1) ClassMap: class1 Type: qos
Referenced by 3 Policymaps
2) ClassMap: class3 Type: qos
Referenced by 2 Policymaps
in this examples the QOS class-maps class1 and class3 which have index 1 and 2 respectively are used by respectively 3 or 2 policy-maps. can't remove them.
I could technically remove this class-map:
20) ClassMap: v6 Type: qos
Referenced by 0 Policymaps
Not used at all.
regards
xander