So many to choose from, but some of my favorites are:
- Yosemite: Rostrum
- Tuolumne: Third Pillar of Dana, Regular
- J-Tree: O'Kelly's or Rubicon
- Needles: Thin Ice (or, for an awesome 5.6 crack try Tree Route!)
- Indian Creek: Well, most of them are better than most cracks on the planet, but I love King Cat
- The Rectory: Fine Jade

This:

www.mountainproject.com/v/best-crack/106025298

Many have already been stated and my list is Cali-centric, but here goes:
Speed of Life, Tioga Pass
Butterballs, Yosemite
Red Zinger, Yosemite
Take any crack pitch on Sunspot or Positive Vibrations
Serenity-Sons (maybe best 5.10 multipitch crack route anywhere?)

Too many to list in the Creek...

single
1. Japanese Gardens, Index, WA (Refering to linking pitch 1&2)
2. New Traditionalist, New River, WV
3. Terminator, Oak Creek, AZ
4. Critic's Choice, Indian creek, UT
5. Black Angel, Tuolumne, Ca (want this in my back yard)

multi
1. Freeway, squamish, BC
2. Sunspot Dihedral, Bridgeport, CA
3. Astroman, Yos, Ca
4. Silk Road, Calavaras, Ca
5. West Face of El Cap, Yos, Ca (wish I could do harder El CAPS)
6. Alaska Highway, Squamish, Ca (Prolly better if linked with the calling)

All of these routes have a good variety of different styles and pure quality crack.

Lifetime goal -- print out this thread and hit the road...

Wunsch's Dihedral

For me
Single Pitch
Terminator- oak creek, Az...
Lifeline* and Red Planet*-Sedona, Az
Optimator* and Learning to Fly*- Indian Creek

Multipitch
Shangrila- Sedona, Az
Alaskan Highway-Squamish
Rostrum (it's ok compared to Shangrila)-Yosemite

The star denotes routes I've been working on but have not gotten clean

I'm still looking for the crack that is nirvana

Damn all of you that listed great cracks that are out of reach for my ability.

excuse station, reservior wall indian creek
steven carruthers memorial, sacred cow wall indian creek
mexican creek, little cottonwood cayon
gold rush, trout creek

Jtree has some good easier cracks..Lighting bolt crack

Center route-Cynicle Pinicle. In the Splat.

Don't forget the Southeast. You know...like some roofs or multiple tiers. Add another dimension to your crack climbing.

Hands down, Shune's Buttress in Zion. Upper crux pitch is a lightning bolt splitter starting with yellow aliens and ending in a few moves of hands with 700 feet of clean air below.

Yosemite: Astroman, Rostrum, Steck-Salathe
Squamish: Grand wall, Freeway
Index: Godzilla, Japanese Gardens, Thin Fingers
Josh: The Flake
Suicide/Tahquiz: The Vampire

Hard to believe that nobody has mentioned The Line at Lover's Leap, or Pear Buttress at Lumpy...two great routes for us mere mortals.

I climbed The Line ('was dragged up' is more like it) on my very first day of climbing...there are probably still pieces of my skin up there somewhere.

Or...

<<< Invalid image id: 107523410 >>>

drool...

Veedauvoo - Horns Mother and Left Torpedo Tube
Indian Creek - Big Guy and Low Cholestrol
South Platte - Prairie Dog Crematorium
Potash Road - Offwidths are Beautiful

Yep all are off widths!!!!

Godzilla, P2 of City Park, and the stoutest 10d anywhere, Sloe Children. Every pitch is progressively harder and classic at the grade. Index is my favorite crag, can't wait to camp out there this summer.

If you don't mind cleaning moss there are plenty of classics that don't get done often enough.

Damn, there are some good ones on here. I gotta add the upper pitches of Outer Space in Leavenworth, WA. Splitter hand crack and enough chicken heads that your feet don't hurt by the end of it.

Gotta say, the third pitch of Turfspreader, on the Cynical is a really gorgeous, perfect 5.8+ in a beautiful spot.

MOONLIGHT BUTTRESS

.. At least it was the most beautiful crack I hav ever *seen* BY FAR!! Blows rostrum and nose outta the water. Never ending fingers in beautiful rock and location.

Even without touching the route absolutely no contest. Go take a look and u will agree. Unfortunately I was training for speed climbing and rapped then jugged the entire route LOL!

Favorite single pitch crack - nine lives@ cat wall (indian creek)

Strate Raza that hangs out in the Squire Lounge has got some sheeze that will blow your mentalz

I thought I'd replied to this already, but I guess not.

Camhead has already listed the best cracks that I've fallen off of, and the rest of you have listed a lot that would be on my list. Indian Creek, The Needles and The Spiders Web in the ADKs are the best crack venues I've seen.

A few routes that are not on the list:

The Womb, Looking Glass
Shredded Wheat, Rumbling Bald
Burning Calves, New River Gorge
Spiderwand, New River Gorge
Rod Serling Crack, NRG
Welcome to Beauty, NRG
Pigs on the Wing, Indian Creek (too many at IC to list)
Fine Jade, Castle Valley
N. Face of Castleton, CValley
Hospital Corner, Lover's Leap
Tombstone Terror, LLeap