Toot
Toot
Cueball: I don't mean to toot my own horn, but I was first in my class at Caltech.
Black Hat: Really? I don't mean to toot my own horn, but BRAAAAAAP! [Cueball falls backward as Black Hat sounds an air horn in his face.]
[A picture of an air horn.] Air horns: Worth carrying around your entire life for those few perfect moments.

"Toot my own horn" is an idiom meaning to brag. Cueball here is using this idiom to mean that he is not bragging, although he obviously is. However, Black Hat , being the classhole he is, takes this idiom literally and toots (blows) an air horn . An air horn is a horn attached to a can of compressed air, and at close range is extremely loud. Cueball is obviously surprised, as he was expecting Black Hat to start bragging instead of making an extremely loud sound with an air horn.
Black Hat's actions could also be interpreted as punishment of Cueball, who began by claiming that he didn't want to boast about his accomplishments, but then did so anyway. Or he could just be proving that he is a classhole by 1'upping Cueball.
The title text refers to the Vuvuzela , which is a noise-generating instrument , mainly used for making noise at soccer matches in South Africa. This comic was published during the 2010 FIFA World Cup in South Africa, and the constant buzzing from vuvuzelas throughout the matches attracted attention and controversy.
Cueball: I don't mean to toot my own horn, but I was first in my class at Caltech.
Black Hat: Really? I don't mean to toot my own horn, but BRAAAAAAP! [Cueball falls backward as Black Hat sounds an air horn in his face.]
[A picture of an air horn.] Air horns: Worth carrying around your entire life for those few perfect moments.
