The Alchemist is the most underrated producer at this time. He makes sick beats. Sometimes, but rare, he raps also. First, he started as a part of duo The Wooligans. After that he made some work for Cypress Hill and that brought him out of anonimity.
Some haters says that he just loops beats but if you are familiar with his work you will know that is not true. As far as I know he is Eminem's official DJ. That, on my oppinion, was his step down considering his devotion to more street and underground music. Hope to see him still making good music. Some of his best known work are:
50 Cent - Animal
Big Noyd feat. Mobb Deep - Shoot Em Up Pt. II (Bang Bang)
Big Pun feat. Tony Sunshine - Mama
Capone-N-Noreaga feat. Foxy Brown - Bang Bang
Chinky - Strength Of Pain
Cormega - Fallen Soldiers (Remix)
Cormega - The Legacy
Cypress Hill - Bang Out
Cypress Hill - Rap Superstar (Remix)
Cypress Hill - Tequila Sunrise (Remix)
Cypress Hill feat. Tego Calderon - Latin Thugs
D12 - Get Back
Dilated Peoples - Annihilation
Dilated Peoples - Back Again
Dilated Peoples - Heavy Surveillance
Dilated Peoples - Live On The Stage
Dilated Peoples - Marathon
Dilated Peoples - The Platform
Dilated Peoples - Worst Comes To Worst
Dilated Peoples feat. Devin The Dude - Poisonous
Dilated Peoples feat. Prodigy - Thievz
Everlast feat. B-Real - Deadly Assassins
Fat Joe feat. Baby, Scarface & Tony Sunshine - Bust At You
Fat Joe feat. Remy Martin - Definition Of A Don
Ghostface Killah feat. Raekwon The Chef - The Watch
Ghostface Killah feat. Trife Da God & Superb - The Juks
Guru feat. Timbo King, Killah Priest & Black Jesus - In Here
Havoc - The Illest
Illa Ghee - What's Good
Infamous Mobb - Special Edition
Infamous Mobb feat. Prodigy - Mobb Niggaz (The Sequel)
Jadakiss - We Gon' Make It
Lloyd Banks - Bangers
Mobb Deep - Get At Me
Mobb Deep - Got It Twisted
Mobb Deep feat. Infamous Mobb & Chinky - Thug Muzik
Mobb Deep feat. Kool G Rap - The Realest
Nas - Book Of Rhymes
Nas - Mastermind
Nas feat. Lake - Revolutionary Warfare
Nas feat. Prodigy - Tick Tock
Prodigy - Keep It Thoro
Saigon - I'm Gone
Sheek Louch - Turn It Up
Sheek Louch feat. Ghostface Killah - Movie Niggaz
Snoop Dogg feat. E-White & Soopafly - Hey You!
Styles P - A Gangster And A Gentleman
Terror Squad - '99 Live
Terror Squad - Bring It On
Tha Eastsidaz feat. Kokane - Friends
Tha Eastsidaz feat. Snoop Dogg, Mobb Deep & Kokane - Connected
The Alchemist feat. Prodigy, Nina Sky & Illa Ghee - Hold U Down
The LOX - The Essence
The Riflemen - Riflez
T.I. feat. P$C - Pimp Squad
Tragedy Khadafi feat. Littles - Stay Free
Tragedy Khadafi feat. Jinx - Love Is Love