Comment Most popular votes could be rather unpleasant... (Score 1) 405
In a vacuum, you can actually be conscious for about fourteen seconds. You can feel the moisture boiling on your tongue even - if a space-suit failure during a NASA test is in any indicator. There is no inner boiling or exploding or instant freezing - you die primarily from asphyxiation. If you try to hold your breath you will suffer an embolism, so that can be an extremely painful fourteen seconds. Once you lose consciousness, a few minutes before you reach critical mortality. Fourteen seconds may seem brief - but when you know you're going to die, they can be like fourteen minutes.
A robotic termination can be quite messy and imprecise. No guarantee of immediate fatality - which means you're left gasping for air with an open-chest wound while you bleed out inside, dying either from eventual asphyxiation or blood loss, which can take minutes.
I think perhaps getting lost in a transporter buffer would be about the most painless sci-fi way to go. Or the War of Worlds poof.