Simple Sentences:
* The color of the car was unimportant to her.
* His opinion on the matter was unimportant to me.
More Complex Sentences:
* While the details of the party were unimportant, the overall feeling of joy was essential.
* The minor details of the report were unimportant, but the main findings were crucial.
* She realized that her initial concerns were ultimately unimportant in the grand scheme of things.
Sentences with Emphasis:
* It's incredibly unimportant to me what people think about my clothes.
* The outcome of the game was completely unimportant to her.
Sentences with Contrasting Ideas:
* The deadline was unimportant, but finishing the project was crucial.
* Although his performance was disappointing, it was ultimately unimportant compared to the overall success of the team.
Remember that the meaning of "unimportant" is subjective and depends on the context.