。
I came up with a good idea, you know.
Literal
I [topic-は] good idea [object-を] hit-upon [emphasis-よ].
思いつく is a compound verb: 思う ('to think') + つく ('to attach, to hit'). Together it means 'an idea hits/strikes one' — i.e. 'to think of, to come up with.' Often used for sudden inspiration. The final よ shares the news with the listener as fresh information.