I would do a german fairy tale thing and pry off your thumbs. Then while you were in total agony I would do the misery thing and hobble both of your ankles. Being comfortable in the fact that you could not escape, I would go and prepare a very special stew and 'finger' sandwiches. Gently forcing you to eat them with the pliers, I would then afterwards do the Jeoffry thing and rip out your tongue. And the Reek thing, but we won't get into that.
Afterwards, assuming that you were begging for death (I mean you cannot speak and I would think it would be hard to write without thumbs), would take out my wand, crucio you for a bit, and perform a nice avada kedavra.