僕が何を怖がるっていうんだ?
It's a rhetorical question (修辞疑問文). It means/implies "What would I be afraid of? -- No, I would be afraid of nothing!"
僕が何を怖がるっていうんだ?
It's a rhetorical question (修辞疑問文). It means/implies "What would I be afraid of? -- No, I would be afraid of nothing!"