This is my schedule for a "Batman" day long marathon, well 6am to 12am. (For most of the episodes, I'll list who the main villain is):

6:00am - "On Leather Wings" (Man-Bat)
6:30am - "Nothing to fear" (Scarecrow)
7:00am - "The Last Laugh" (The Joker)
7:30am - "Pretty Poison" (Poison Ivy)
8:00am - "Two-Face, Part 1" (Rupert Thorne)
8:30am - "Two-Face, Part 2" (Rupert Thorne, Two-Face)
9:00am - "I've Got Batman In My Basement" (The Penguin)
9:30am - "Heart of Ice" (Mr. Freeze)
10:00am - "Beware of the Gray Ghost" (The Mad Bomber)
10:30am - "Feat of Clay, Part 1" (Daggett)
11:00am - "Feat of Clay, Part 2" (Clayface)
11:30am - "Fear of Victory" (Scarecrow)
12:00pm - "Mad as a Hatter" (The Mad Hatter)
12:30pm - "Cat Scratch Fever" (Catwoman)
1:00pm - "The Strange Secret of Bruce Wayne"
1:30pm - "If You're So Smart, Why Aren't You Rich?" (The Riddler)
2:00pm - "Almost Got 'Im"
2:30pm - "The Man Who Killed Batman"
3:00pm - "House and Garden"
3:30pm - "Time Out of Joint"
3:00pm - "Bane"
3:30pm - "Second Chance" (Two-Face)
4:00pm - "Harley's Holiday"
4:30pm - "Make 'Em Laugh" (The Joker)
5:00pm - "Sins of the Father" (First Tim Drake episode)
5:30pm - "Cold Comfort" (Mr. Freeze)
6:00pm - "Never Fear" (Scarecrow)
6:30pm - "Joker's Millions" (The Joker)
7:00pm - "Love Is a Croc" (Killer Croc)
7:30pm - "Over the Edge"
8:00pm - "Cult of the Cat" (Catwoman)
8:30pm - "Old Wounds"
9:00pm - "Legends of the Dark Knight"
9:30pm - "Mad Love"
10:00pm - "Beware the Creeper"
10:30pm - "Judgment Day" (Two-Face) - Series Finale


I haven't watched every episode so I'm sure there are some great ones I'm leaving out. However, what would your Batman marathons be like? They can also include the movies (Mask of the Phantasm, Sub-Zero, Batman/Superman, Mystery of the Batwoman).