Anti-Climax Boss: After the grueling Metal Sonic battle, you're treated to a 15-second fight with Dr. Robotnik in his Powered Armor, who can almost effortlessly be taken down, as he can only do a PPP combo and a throw. Combine this with the fact that you start with a perma-Hyper Mode to encourage you to really let loose on him or the Death Egg II will self-destructwith you in it if you have more HP than Robotnik when time runs out. What's odd is that Robotnik -does- have a full (and quite deadly) moveset, as using cheats to play as him reveals, he just doesn't use it because it would be unfair considering the time constraints.
Cult Classic: While not the most well-received spin-off of the Sonic the Hedgehog series (and more-or-less a "Fighting Vipers with Sonic the Hedgehog characters" game), it does have a cult following for being an obscure Sonic the Hedgehog fighting game. There are small competitive and speedrunning scenes for the game.
Bean and Bark after they were reintroduced in Archie's Sonic The Hedgehog comics and were written as hilarious, bounty hunting Heterosexual Life-Partners.
When it was discovered that an incomplete version of Honey from Fighting Vipersin the form of a cat was hidden within the game's files, she became one of the most popular characters within the Sonic fandom, arguably more than her original human counterpart, an established Ensemble Darkhorse in her own Cult Classic series and one of Sega's most popular sex symbols. Despite being a Guest Fighter, many fans have expressed wanting to see cat Honey appear in the main Sonic canon. Perhaps acknowledging her popularity, upon the announcement of the Model2 Collection Updated Re-release, Honey was shown to be completed as a hidden playable character. She was also heavily requested by fans to appear in the comic book series, and finally appeared in the comic's adaptation of the game, retaining her human counterpart's role as a fashion designer who joins a fighting tournament to promote her line.
Fridge Logic: Of course there's the infamous 8 Chaos Emeralds bit, which was an excuse to have eight main fighters, but then you never actually fight a character who has the eighth emerald (logically this would be you, but you don't actually start with any Emeralds); instead your character gets cloned by Dr. Robotonic and you get the last emerald from the resulting eighth fight. So.. One of your emeralds was cloned too?
Game-Breaker: Sonic's spin-dash move, which deals heavy damage and is fast-hitting.
It's Easy, So It Sucks: The most common complaint against the game is that it's very easy compared to most fighting games. Some even claim that you can win by holding down one button.
Older Than They Think: This was officially the first game to give Amy her iconic Piko-Piko Hammer. While intended as a gag, it stuck, and became her Weapon of Choice and she's rarely seen without it. Fans unfamiliar with the game generally assume Adventure did it first.
Polished Port: The Model2 Collection's Updated Re-release on PlayStation Network and Xbox LIVE Arcade, as it has the Dummied Out characters added (though only a few, not all of them), online multiplayer, and a Sound Test function by using the trigger buttons on the controller.
Before him, Bean (the seventh opponent you face, before Sonic and Metal Sonic) is usually seen as a major difficulty spike compared to the opponents you face before him.
Vindicated by History: On its release, it was one of the most critically reviled spin-offs of the franchise due to its unbalanced cast, overly simple gameplay, and due to it being perceived as a poor Follow the Leader attempt to cash-in on the popular fighting game trend at the time. As time has gone by, nostalgia for the game has greatly lessened the initially poor reception, and it is now considered a fun spinoff with unique characters and gameplay. While it's ultimately a pretty shallow button-masher, it's still a lot of fun with friends and the goofy animations still make it amusing.