Among the enormous advantages Europeans had over indigenous societies in the colonization of the Americas, technology stands out. According to Guns, Germs, and Steel, what were the most important European advantages in technology?
The best place to find an answer to this question is in Chapter 3 of the book. There, Diamond discusses the reasons why the Spanish were able to conquer the Incas. The chapter includes a discussion of the main technologies that Diamond feels were important. This discussion begins on p. 74 in the paperback edition of the book.
On p. 74, Diamond talks about how weapons technology was very important. He mentions that the Spaniards had steel weapons, including swords. He mentions that they had steel armor. He notes that they had guns. All of these were much more powerful than the equivalents that the Incas had. (Diamond also mentions horses, but they are not really a technology, even if technologies like stirrups are used to ride them.)
On p. 78, Diamond talks about “maritime technology” that the Europeans had and the Incas did not. These technologies were important because they allowed the Europeans to travel to the Americas where the Americans could not travel to Europe. The only technology that Diamond actually mentions is ships.
On this same page, Diamond notes that writing was very important in allowing the Spaniards to dominate the Incas. This may or may not count as technology in your view. Writing allowed the Spaniards to have much more information than the Incas could.
These are the most important technological advantages that Diamond talks about in Chapter 3.