Snivy can be summoned from a regular Poké Ball, and will use the move Razor Leaf. The move sends projectiles doing minimal damage consistently in one direction.
Along with Ekans and Onix, this Pokémon is considered to be a snake Pokémon, even though it has two legs. When it evolves into Serperior, however, it sheds those legs. In Smash Bros., Snivy unleashes Razor Leaf on fighters, sending sharp leaves flying and damaging anything in range.
In its trophy description for the 3DS version, Onix is misspelled as "Onyx".