Anybody with sysadmin rights can do it. Or the owner of the job. Or anyone with the SQLAgentOperator Role.
As far as a list. Not off the top of my head. But those would be able to accomplish it.
Keep in mind that my experience shows that the sysadmin role often includes the machine admins it is entirely possible they did it. However, doesn't your sql agent job log show who cancelled it?
CEWII