Two-fer today. Lucky you.
5. Clay Kirby (0.5 WAR)
After the top end of this list, it thins out pretty drastically. Clay Kirby has a World Series ring, though. He was great in 1974, and won the ring in '75 with a less great season. He had a 4.72 ERA, but made 19 starts for that team. He tragically passed away of a heart attack at age 43.
4. Jonny Gomes (0.8 WAR)
He's the most recent guy of note, so he wins. Gomes spent 2 1/2 seasons with the Reds, with his 2009 year being one of his best in baseball. He slashed .267/.338/.541 that season, but his value is a bit skewed by his rough defense. He won the World Series last year with not the Reds.
3. John Franco (14.0 WAR)
Franco broke in with the Reds in 1984 as a 22-year-old, and pitched with them for 7 seasons. He was their closer at the tail end of the '80s, and made 3 All-Star teams with Cincinnati. He'd go on to play for the Mets for roughly the rest of time.
2. Jim O'Toole (21.3 WAR)
Jimmy O! O'Toole pitched for the Reds from 1958 to 1966, most notably as the ace of the staff that made it to the 1961 World Series. He went 19-9 that year with a 3.10 ERA and a career high 178 strikeouts. He put up a lot of really great years with the Reds, and as a Reds Hall of Famer who still lives locally, shows up to lots of team events and reunions. He also crashed a Red Reporter outing once, and could not have been cooler. Rock on, Jimmy O.
1. Bucky Walters (37.7 WAR)
Walters came to the Reds in 1938, and pitched for them for 11 seasons, including the 1940 championship team. He made 4 All-Star teams with the Reds, and was the 1939 MVP, one of very few Reds to achieve that honor. He went 27-11 with a 2.29 ERA that year, with 31 complete games and over 300 innings pitched. He led the league in all of those categories, as well as strikeouts and WHIP too. Arguably, it's the best pitching season by a Red in the modern era. #31 in your programs, #1 in your hearts, Bucky Walters.