Ill start with Notorious BIG "Juicy" one of the best hip hop songs ever in my opinion

Doug E. Fresh ft. Slick Rick-La Di Da Di
Beastie Boys-Paul Revere
Grand Master Flash-The Message

Fugees - Ready or Not

Slick Rick - Children's Story
Nas - It Ain't Hard To Tell
A Tribe Called Quest - Check The Rhime
Eric B. & Rakim - Eric B. Is President
Busta Rhymes - Woo Hah!
De La Soul - Me Myself & I
Fugees - Fu-gee-la

Those instantly come to mind but there are so many othe great ones.

missy elliot " the rain "

busta rhymes "Put your hand where my eyes could see"

Mariah Carey Feat. ODB Fantasy(Remix)

2 pac feat. Dre California Love

LL Cool J - Doin It
Lil Kim - The Jump Off
Nas - If I Ruled The World
Jay-Z - Encore
DMX - Stop Drop (Ruff Ryders Anthem)
Puff Daddy - It's All About The Benjamins
Wu Tang Clan - Gravel Pit

Ooh, that gives me an idea. Best Hip-Hop/R&B collabos.
-Mariah Carey feat. ODB - "Fantasy" Bad Boy Remix
-Mariah Carey feat. Trackmasters - "Underneath The Stars" Drifting Remix
-Mariah Carey feat. Mocha & Camile - "I Still Believe" Stevie J Remix
-Vanessa Williams feat. Black Sheep - "Work To Do" Super Dope Remix
-Jody Watley feat. Eric B.& Rakim - "Friends"
-Mary J. Blige feat. Greg Nice - "You Remind Me" Daddy Hip-Hop Mix
-Mary J. Blige feat Notorious B.I.G. - "Real Love" Remix
-112 feat Notorious B.I.G. & Mase - "Only You" Bad Boy Remix
-Aaliyah feat. Timbaland - "Hot Like Fire" Timbaland's Groove Mix
-Mona Lisa feat. Lost Boyz - "Can't Be Wasting My Time" One Dread One Ball Head Version

So many more as well.

The Rain <333333333333333333 (that's one of Missy's best songs EVER)

Kevin Federline "Lose Control"

Junior Mafia- Get Money

Notorious Hypnotize

OMG Rappers Delight - Sugarhill!!!!!!!!

2Pac - Changes

I'll be compiling a list soon

Khia - ****ing Me Tonight
Khia - For The Love Of Money

2Pac - I Get Around
LL Cool J - Mama Said Knock You Out
Dr. Dre - Nuthing But A G Thang
Snoop Dogg - Gin and Juice
Coolio - Fantastic Voyage

what about

Gansta Paradise- Coolio
Salt N Peppa- Shoop

Outkast - B.O.B.(Bombs Over Baghdad)
Beastie Boys - Sabotage
Eminem - Lose Yourself
Dr. Dre and Snoop D O Double G - Nothin' But A G Thang
Public Enemy - Fight The Power(The coolest rap song ever made. Deny it and you will be smited by yours truly.)
Snoop D O Double G - Who Am I?(What's My Name)
Run DMC - It's Tricky/Kings Of Rock
LL Cool J - Mama Said Knock You Out
Blondie - Rapture

Just a few, anyway.

Jay Z- Hard Knock Life. I want to hear Reasonable Doubt.
2 Pac had a bunch of rap classics.
Snoop in the 90s was on it with Sippin on Ginin Juice and other tracks.
Biggie was just the man..
Missy was also on it with The Rain and other tracks in the late 90s.

One artist I never was into and dont know much bout is Nas.... dont know why.

Missy Elliot feat. Nelly Furtado ~ Get Ur Freak On (Remix)

Beyonce - Crazy In Love/Baby Boy
Aaliyah - Try Again/More Than A Woman/One In A Million
Mya - Case Of The Ex
2Pac - Changes
TLC - Unpretty/No Scrubs/Red Light Special
B.I.G. - Hypnotize
Mary J. - My Life/Be Without You
Mariah Carey - Emotion/Honey/Fantasy/Dreamlover/The Roof
Missy Elliott - Get Ur Freak On
Brandy - Almost Doesn't Count/Have You Ever
En Vogue - Don't Let Go
Aaliyah - Like This Like That/Miss Thang/Angel Of Mine
Dre - Forgot About Dre
Eminem - Guilty Conscience/Role Model/The Way I Am
Jay-Z - Hard Knock Life
Coolio - Gangsta's Paradise