I go d5 to make a countergambit; pretty interesting and wrecks the KG player's plans :)
I encounter this frequently: I always take this pawn immediately via 3. exd5 then when 3. ... Qxd5 4. Nc3 I keep the pressure on and continue with even more momentum!
It has foiled my plans a few times, but I've learned to defend against it - basically take the pawn right away!
I go d5 to make a countergambit; pretty interesting and wrecks the KG player's plans :)