Hulk Hogan comes in to voice Angel De LaMuerte, and Sasha Grey (famous for her...other works) voices Viola DeWynter.
The Cockney voice option in The Third is provided by Robin Atkin Downes.
Yuri Lowenthal puts on a Fake Brit voice for Syndicate hacker Matt Miller (Which makes him the second Gang leader he has voiced, since he voiced Shogo Akuji in 2), and his wife Tara Platt acts as the protagonist's Fake Russian female voice.
The second game has a fair amount of references to anime and manga, particularly as far as the Ronin are concerned. Three of the bikes in the game are named Kenshin, Tetsuo, and Kaneda; the latter two are references to Akira, the former, possibly Rurouni Kenshin. Shogo Akuji and his father Kazuo are named after Shogo Kawada and Kazuo Kiriyama from Battle Royale. Finally, both Shogo and Kazuo are voiced by well-known anime V As: Yuri Lowenthal and Steve Blum, respectively.