Kaufusi was tipped as a possible surprise selection in the squad after his performance in Sunday's NRL grand final when Melbourne thrashed the North Queensland Cowboys.
"I'm just dumbfounded by people tossing my name up when there are so many great players in front of me," Kaufusi said before the squad was unveiled.
Slater won the Clive Churchill medal for the player of the NRL grand final, capping a remarkable comeback season following injuries which sidelined him last year and threatened his future in the game.
The other Melbourne players in the squad are Smith, veteran halfback Cooper Cronk, Cameron Munster, Will Chambers and McLean. Cronulla has four players - Wade Graham, Andrew Fifita, James Maloney and Valentine Holmes - as does Brisbane with Hunt, Darius Boyd, Matt Gillett and Josh McGuire.
Boyd has a hamstring injury but is expected to be fit for the World Cup.
Tom Trobojevic's brother Jake is also selected. Cowboys playmaker Michael Morgan was picked as a utility player after spearheading North Queensland to an unlikely run from outside the top eight and into the final. Cowboys and Australia veterans Johnathan Thurston and Matt Scott were unavailable because of long-term injuries.
Australia is the defending World Cup champion and has won the tournament 10 times since its first edition in 1954.
Kangaroos squad
Darius Boyd - Brisbane Broncos
Will Chambers -Melbourne Storm
Boyd Cordner (vc) - Sydney Roosters
Cooper Cronk - Melbourne Storm
Josh Dugan - St George Illawarra Dragons
Andrew Fifita - Cronulla-Sutherland Sharks
Tyson Frizell - St George Illawarra Dragons
Dane Gagai - Newcastle Knights
Matt Gillett - Brisbane Broncos
Wade Graham - Cronulla-Sutherland Sharks
Valentine Holmes - Cronulla-Sutherland Sharks
Ben Hunt - Brisbane Broncos
Felise Kaufusi - Melbourne Storm
David Klemmer- Canterbury-Bankstown Bulldogs
Josh McGuire - Brisbane Broncos
James Maloney -Cronulla-Sutherland Sharks
Jordan McLean - Melbourne Storm
Michael Morgan - North Queensland Cowboys
Cameron Munster - Melbourne Storm
Billy Slater - Melbourne Storm
Cameron Smith (c) -Melbourne Storm
Jake Trbojevic - Manly Warringah Sea Eagles
Tom Trbojevic - Manly Warringah Sea Eagles
Aaron Woods - Wests Tigers