Basso Profondo

Voice archetype: a guy who sings bass. Allow me to rephrase that: a guy who sings BASS, a bass singer's bass, a bass that makes Barry White sound like a tenor.

Basso profondo is the technical term for the lowest of all voices. To qualify, the character must be able to give a tuba a run for its money when it comes to low notes.

Many may be "Oktavists", men who sing a full octave below the normal bass range. Obviously these singers are Always Male — unless they aren't.

Examples of Basso Profondo include:

Film

Voice actor James Earl Jones (the voice of, among others, Darth Vader and Mufasa) is noted for being this.
While not a singer, actor Kevin Grevioux has an extremely deep voice, to the point where many people watching Underworld thought his voice was altered. Not only is Grevioux playing a brutish enforcer (and looks the part), but he's also the one who came up with the idea for the movie in the first place thanks to his degree in microbiology.

Literature

Referenced in Soul Music by the bass guy who says nothing but "Oh, yeeeah". Except when confronted by Susan, when it changes to "Oh, noooooo".

Music

Guinness world record holder for lowest note ever sung and widest vocal range, Tim Storms.
Richard Sterban of The Oak Ridge Boys, most famously on their song "Elvira". Another example is Dream On
Harold Reid of The Statler Brothers
J.D. Sumner of The Blackwood Brothers held the Guinness World Record for lowest human voice.
Thurl Ravenscroft
In the song "North To Alaska" Johnny Horton hits a basso-profondo note ("way up noooooooooorth").
Johnny Cash, at times, too.
Barry Carl, the bass guy from Rockapella
Isaac Freeman of the Fairfield Four.
Paul Robeson, as demonstrated here.
Boris Christoff: the start of this is a good example
The voice type is prevalent in Russian Orthodox chant and other Slavic music. For this reason, a common term for Basso Profondo is "Russian bass."
Parodied in "The Dooright Family" by Ray Stevens, where the bass singer in the titular gospel family band (voiced entirely by Ray) is asked to "go for another octave". He does (by way of studio trickery on Ray, who is a baritone at best in Real Life), causing him to explode onstage.
Noriel Vilela, a Brazilian samba singer.
Michel Bell, Tony-nominated actor-singer and former member of the Fifth Dimension.
Male choir Chanticleer features bass Eric Alatorre, whom you can hear in all his glory in John Tavener's "Village Wedding" (listen for him during the tenor's solo that starts with "let them throw white rice like a spring shower").
One of the background singers on Canadian singer-songwriter Bruce Cockburn's "Anything, Anytime, Anywhere" is an oktavist. Listen particularly at the end.
Paul David Kennamer from Valour Music. His solo starts at 52 seconds in here.
Tom Waits is best known as a basso profondo singer, though in his earlier career he was better known as a smooth-voiced baritone.
Yuri Wichniakov is a particularly low basso profondo, whose lowest recorded note is an E1 during "Evening Bell" at about 4:00 in.
The late Peter Steele of Type O Negative.
Achieved with electronic help by the vocalist on "Oh Yeah" by Yello -- better known as "that 'oh yeah' song from Ferris Bueller."

Western Animation

Much like James Earl Jones, Kevin Michael Richardson, veteran voice actor, is known for this trait, and has used it in a plethora of his voice roles.
Played for laughs in the Dexter's Laboratory episode "Dee Dee Be Deep". Dexter tries to improve his sister Dee Dee's awful singing voice with one of his inventions, but thanks to Dee Dee messing around with it she becomes a very exaggerated bass. While she doesn't get into the school choir, it works out for her in the end; she joins a Barbershop Quartet instead.