The title says it all! My list is primarily based off of which episodes I most frequently return to.

(In no particular order)

-Will Goes a Courtin' (Season 4)
-Home is where the Heart Attack is (Season 4)
-Def Poet's Society (Season 1)
-Mistaken Identity (Season 1)
-Stop Will! In the Name of Love (Season 4)
-PSAT Pstory (Season 2)
-Will Gets a Job (Season 2)
-Baby Comes Out (Season 3)
-Here Comes the Judge (Season 3)
-Hare Today (Season 6)
-I, Clownius (Season 6)
-Not, I Barbecue (Season 6)
-Burnin' Down the House (Season 6)
-Get a Job (Season 6)
-Blood is Thicker than Mud (Season 4)
-Sleepless in Bel Air (Season 4)
-I Know Why the Caged Bird Screams (Season 4)
-You'd Better Shop Around (Season 4)
-Banks Shot (Season 1)
-Clubba Hubba (Season 1)
-The Lucky Charm (Season 1)
-Knowledge is Power (Season 1)
-Kiss My Butler (Season 1)
-Strip Tease for Two (Season 2)
-Eyes on the Prize (Season 2)

every episode besides Will being shot

the best ones are when Will and Carlton take uncle Phil to court, the one where Will joins the basketball team, Banks Shot, the one where Carlton goes to Compton and the one where the mob hitman is after Will

Every episode from the sixth season but my favorite was I,clownius that episode made me laugh hard i cant watch the episode without laughing haha i wanted to see a 2 part I,clownius the revenge part 2

http://www.youtube.com/watch?v=7RGow_trmiU

Somebody alright mentioned mine but I'll add
Phil's mom visits
Will hires an ex con
Showbiz madam trial
Will sleeps with his girlfriends mother
Carlton loses his virginity