The name is Robert Gibson.
If there is a name I cannot read – which happens fairly often – then I will turn to what I can read first, and see if that helps to track it down. In this case, given this is an 1899 death certificate, the 1901 Irish census seems a good starting place.
We know his address is 27 Williamstown. So Blackrock area of Dublin. By searching this area I came across:
Robert Gibson, age 34, living in Blackrock, house number 27
http://www.census.nationalarchives.ie/pages/1901/Dublin/Blackrock/Rock_Road__Part_of_/1313175/
You can view the relevant images there to determine whether this is the correct man, but pieces seem to fit. Sometimes to read old documents you need to reverse-engineer until you can work out the original text, which then often becomes obvious. A word of caution, however, to make sure you are not just seeing what you want to see.