Is it safe to touch the ground pin when using this adapter?
Edit: just to clarify, it's from a 60w laptop power brick.
You might get a tingle from EMI Y-caps but it shouldn't be unsafe to touch the ground pin assuming everything else is in order.
However, the unsafe part of this is that your ground pin is now not grounded, and the chassis of whatever equipment it is powering could become hot in the case of a fault. That's the unsafe part about using the adapter in the manner you're showing. If you do use it that way be sure to plug it in to an outlet with ground-fault protection.
That's the earth pin for your appliance. It's presence indicates that there is a metal body on the appliance. Grounding of the appliance may be essential to protect the user against internal faults. That pin will be at the same voltage as the appliance. In the event of a major fault both the appliance and that pin may be live.
For further insight on grounding see my answer to In any electrical equipment having single ph 230 v ac supply ,if neutral and earth wire exchanged then what will be the consequence.