Here are some possible translations depending on the context:
Informal and playful:
* Petit saucisson: This literally translates to "small sausage," and is the closest you'll get to the playful tone of "weenie."
* Saucisse miniature: Similar to the above, but more descriptive of its size.
Derogatory:
* Peureux: This means "cowardly" and can be used in a similar way to "weenie" to insult someone.
* Froussard: Another word for "coward" that carries a slightly more humorous tone.
* Lâche: This word is more serious and means "cowardly" or "weak."
Context matters:
* If you are referring to a specific type of sausage, like a hot dog, the best translation would be hot-dog (pronounced as in English).
Ultimately, the best translation depends on the specific context and the tone you want to convey.