You'll burn yourself first - actually you can get a jolt, if you manage to get close to the pins when you pull the tube it you may get a flash of HT!
The old trick of leaving standby ON and turn the power off leaving a chord hanging on the guitar. Can help discharge dangerous voltages quickly. It drains the charge in the filter caps.
I usually learn the hard way on things like this.......if it's an old amp watch the top of the filter capacitors.....the old ones weren't always insulated (got shocked twice on an old Orange, first time I thought 'what was that? so touched it again....dumb!)