When people want to describe marketing, tactics, or warfare, they should use the latter of these two homophones. Although the former makes for some amusing mental pictures.
Correct usage, in other words: guerrilla marketing, guerrilla tactics, and guerrilla warfare.
Gorillas are generally nicer than guerrillas -- if I got lost in a jungle, I'd rather meet the gorilla. What that says about the marketing, the tactics, and the warfare, I leave it to yourselves to determine.