Let's talk about Darlington transistors...

[Plexi]

I'm a huge user of the KSP13/14 (MPSA13) transistor: I use them in almost every project... most in the output stages.

What about:
MPSA28/29
MPSA63/64

Another one?
Experiences?

[EBK]

I thought this was going to be another version of "The talk."

"You see, son, when one bipolar junction transistor loves another bipolar junction transistor very much . . . ."

[PRR]

TIP120

[LightSoundGeometry]

one of my best sounding rangemasters was a darlington pair

[antonis]

TIP120

"Golden Antiquity"

Was included in every self respected charger...

[Groovenut]

"Oh darling-ton, please believe me. I'll never do you no harm"

It must be Friday....

I love me some Darlingtons, especially in Fuzz. I dont really have any thing constructive to add though. MPSA13/18 seem to be may fav in a single, though I am not apposed to using a duo of 2N3904s either

[duck_arse]

I dont really have any thing constructive to add though.

me either. MJE800. small power. not helpful.

[GibsonGM]

It must be Friday....

Yes, but it's not after 5:00 PM...

[Groovenut]

It must be Friday....

Yes, but it's not after 5:00 PM...

Well, as the song says, it is somewhere....

[GibsonGM]

Well, as the song says, it is somewhere....

[Transmogrifox]

Main features of the darlington come to mind:
Really high input impedance.
2 diode drops Vbe.
Really high gain (can be more susceptible to noise and oscillations depending how/where they are used).
Harder clipping at cut-off.

These features can be an advantage or a disadvantage, but you do have to keep in mind that bias point in any circuit designed for a regular bipolar needs to be properly adjusted before you pass any judgements about whether it is an improvement. 

Advice for getting the bias worked out with a 6 pack on a Friday:
2 for planning
2 for execution
2 for testing

Make sure you post about how it worked out sometime before midnight while it's still awesome.

[Plexi]

Bump for a observation!
MPSA63: hfe from 500 to 1500, similar to MPSA18.
MPSA14: 10k min
MPSA12: 10k to 20k