Nokia's banana phone and Matrix comes to mind. I assume it was a product placement or they just picked what at the time was a good looking phone, though it seems odd now.
The Nokia 8110 is the one used in the Matrix. The later model, the 7110, was spring loaded. I still have mine. The spring broke, which is a bit frustrating. At the time it was a really nice phone though.
It helps to remember what phones look like at the time. They were all fairly ugly and blocky. The spring loaded mouthpiece was fairly cool looking. Of course, it doesn't exist. That phone never had a spring in it. That was a modification for the movie and I'm fairly certain you couldn't make out the logo or brand. So I'm guessing this probably wasn't product placement. Imagine the angry customers flocking to the store to see that the phone doesn't do what it did in the movies.