If you know about the "about:config" thing, you might want to set these to "false" and remove those that don't toggle.
browser.newtabpage.activity-stream.feeds.telemetry
browser.newtabpage.activity-stream.telemetry
browser.ping-centre.telemetry
toolkit.telemetry.archive.enabled
toolkit.telemetry.bhrPing.enabled
toolkit.telemetry.enabled
toolkit.telemetry.firstShutdownPing.enabled
toolkit.telemetry.hybridContent.enabled
toolkit.telemetry.newProfilePing.enabled
toolkit.telemetry.reportingpolicy.firstRun
toolkit.telemetry.server
toolkit.telemetry.shutdownPingSender.enabled
toolkit.telemetry.unified
toolkit.telemetry.updatePing.enabled
experiments.activeExperiment
experiments.enabled
experiments.supported
network.allow-experiments