The dihalide and pseudohalide radical anions, strong one-electron oxidants, can be selectively generated in aqueous solutions by pulse radiolysis. Radiolysis of salts of the bulky 1-butyl-3-methylimidazolium cation with Cl−, Br−, SCN−, and N3 − anions allows efficient generation of the same species (Cl2 •−, Br2 •−, (SCN)2 •−, and N6 •− radical anions) also in neat ionic liquids and in nonaqueous solvents with the addition of small amounts of the salt. The oxidative power of dichloride radical anion, lowered in the dichloromethane as compared to the aqueous solution, remains sufficient for oxidation of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD, 2 k = (2.0 ± 0.1) × 109 M−1 s−1), phenothiazine (PZ, 2 k = (2.1 ± 0.1) × 109 M−1 s−1), 10-methylphenothiazine (MPZ, 2 k = (9.3 ± 0.1) × 107 M−1 s−1), and 3-methylindole (scatole, SCT, 2 k = (6.8 ± 0.1) × 107 M−1 s−1). It diminishes on going to Br2 •− (reacts only with TMPD, 2 k = (5.4 ± 0.3) × 108 M−1 s−1, and PZ, 2 k = (4.8 ± 0.3) × 108 M−1 s−1) while (SCN)2 •− and N6 •− radical anions oxidize only TMPD, 2 k = (5.1 ± 0.5) × 108 M−1 s−1 and 2 k ∼ 108 M−1 s−1, respectively.