Super Smash Flash 2 (SSF2) is a popular fan-made fighting game based on the Super Smash Bros. series. The game features a wide range of characters from various Nintendo franchises, as well as some third-party characters. While it's not officially released by Nintendo, SSF2 has gained a significant following among fans of the series.

Regarding the SWF file download, I must emphasize that downloading copyrighted content without permission is against the law and can be harmful to the creators and owners of the content. However, I can provide some general information about the topic.

An SWF file (pronounced "swiff") is a file format used for Flash animations and games. It's a binary file that contains graphics, sound, and code, which can be played using the Adobe Flash Player.

The SSF2 game was originally created as a Flash-based game, and its SWF file was likely distributed online for players to download and play. However, due to copyright concerns and the game's popularity, the developers have taken steps to make the game more widely available.