Methyl lithium ($CH_3Li$) is an organolithium reagent which acts as both a strong nucleophile and a strong base.

1. Nucleophilic Addition: Typically, $CH_3Li$ attacks the carbonyl carbon to form a tertiary alcohol (1-methylcyclopentanol) after hydrolysis. However, this product is not listed in the options.
2. Acid-Base Reaction: Cyclopentanone possesses acidic $\alpha$-hydrogens adjacent to the carbonyl group. Since $CH_3Li$ is a very strong base, it can abstract an $\alpha$-proton from cyclopentanone.

$\text{Cyclopentanone} + CH_3^- \rightarrow \text{Cyclopentanonyl Anion (Enolate)} + CH_4$

Given the options provided (Anion, Cation, Radical), the formation of the Cyclopentanonyl anion via the acid-base pathway is the correct answer expected in this context.