There are only five well-documented fatal lightning strikes on giraffes between 1996 and 2010. But due to the population of the species being just 140,000 during this time, it makes for about 0.003 lightning deaths per thousand giraffes each year. This is 30 times the equivalent fatality rate for humans.
Pic by Luca Galuzzi
While that's true and what I'm about to say could be legend rather than reality, I grew up being told that giraffes also tend to go to the top of a hill during storms, making them more likely to be struck by lightning.