Can I legally use the name of a product as the title of a movie.

No, you can't. Wii is a trademarked product of Nintendo, and Nintendo has Wii trademarked and service marked for many goods and services, including filmed entertainment, so they'd likely object that even though your film isn't really about their products and services, your use could confuse their young and unsophisticated audience into thinking that they're the source of the film, and preempt the market for their Wii movies which are actually based on their products and services. They'd also claim that your use "dilutes" their mark by using it to identify a product it doesn't actually provide, and unfairly competes with their own filmed entertainment by misleading the public about what the film is about and who the source is.

You acknowledged that you don't need to use Wii is the film's title, and it's just a reference to one line in the film (which is probably a permissible use), so your use makes it look like you're trading on Wii's popularity to get attention to your film you wouldn't otherwise get if you gave your film a title without a famous trademark in it. That's unfair competition.

As for your determination that your film doesn't defame the product, you don't get to decide that, and further, your reference to the Wii isn't exactly complimentary. As a matter of fact, this is why trademark rightsholders get exclusive rights to their mark, other than nominative fair use uses --so others don't get to decide whether a use is defamatory or not.

A studio or other financier would never fund your film and release it with this name. So unless you intend to release it independently get some "free" publicity by provoking a trademark infringement suit, which is far from free in the end, find another title for your film.

Before you copyright the screenplay and film, hire an IP lawyer to vet the contents, to avoid problems later on.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.

The answer to most of life's questions -- including legal ones -- is maybe. In this case, whether you can use someone else's trademark in the title of your movie depends on the content of the movie.

For example: If the name of your movie was "Wii The People" and it chronicled the advent and consumer adoption of Nintendo's very popular video game of that name then that use would clearly be lawful. But if the movie is about the US Constitution and our founding fathers then such use would very likely not be lawful. The first extreme is lawful because there's simply no other way to name the product that your movie focuses upon (and so your use is not a "trademark use" at all) while the second is likely not lawful because you're simply using Nintendo's trademark to grab the attention of movie-goers.

The content (and character) of your movie will fall somewhere in between -- and so, w/o more details no one can tell you whether using the trademark that you have in mind would be lawful.

But that issue is almost secondary. If the trademark owner is a large company and learns about your use of its trademark it will take action -- perhaps only via an internal analysis of your use but it may just send you a cease and desist letter or skip that step and file a lawsuit. In short, you'll be on the company's radar screen (all large companies have active trademark policing efforts that scour publications and the internet for others' use of their trademarks).

Two other things: if you have insurance for your movie the carrier will demand that you "clear the rights" to use all the intellectual property owned by others that appears in your movie (which includes your title). You may have to tell them that you have not done so (if relying on the principle of trademark "fair use" to use the trademark). You may also run into problems with venues (including film festivals) that do not want to run the risk of legal trouble -- for them -- of showing a movie with a title that may infringe someone's trademark rights.

You have much to consider. Hire an intellectual property attorney to help you. Good luck.

Query: how about playstation would the same apply. The title real title is "The playstation killed the puppet"

Answer: Now it's time for you to hire an attorney. Those of us who take the time to answer questions on this site do so to provide folks with (free) general information - not to serve as the questioner's attorney. Also, you should not publicly disclose any further specific information about your particular project. Good luck.