Which interfaces are you monitoring on your switches?

I am just looking for a little advice on what interfaces are important to monitor on a switch.  We are currently monitoring the uplink interfaces on each switch.  The interfaces that we are monitoring have "sflow forwarding" enabled (foundry uses 'sflow') on the switch itself.  Are there any other interfaces that should be monitored?  I know it is a hard question to answer since you don't know our infrastructure.  What interfaces are of importance to your company/work?  Thanks in advance!