Oy. Now this is the one that will break your back, destroy your eyes and give you carpal tunnel till kingdom come. It's when you make an animated gif by hand screen-capping a video clip frame by frame...not for the faint of heart. This is truly a last-ditch effort, only if all else fail. Please, if you wandered in here on a whim and thought, "Hey! This looks like fun; I'll try this instead of the other tutorials!", please run far, far, far away, and whatever you do, DON'T look back. If you value your life, health and happiness, you need to leave. Now. Have I scared you enough already? ;)
Really though, this tutorial is VERY time-consuming and should only be used if all other methods fail. And even then, you're going to want that animated avatar pretty bad to spend your time on this!

Let's get this torture done with, shall we?

To start off, open up your movie clip in a cappable-player such as QuickTime (Windows Media Player and RealPlayer won't work, to my knowledge). Please, for the love of all that is holy and good, if you have a program that will cap for you, such as PowerDVD, use it. It will cut your time in half and your computer will thank you. Literally. I'll be using QuickTime in this tutorial, but if you have a capping program, you can find instructions on how to use it here.

For this demonstration, I've decided to cap the four Pevensies in the tube station from the PC teaser trailer. The key thing is to keep your clip SHORT. Very short. Remember, you have to cap each frame individually. Scary.

Using your arrow keys, rewind or fast-forward the clip until you get to the start of the part you want. This clip started out with a black screen. Not the best for demonstrations, right?

Using the PrintScrn button on your keyboard, make a screenshot and copy it into a file in Photoshop. If you're using a laptop, you may need to hold down the Function key while pressing PrintScrn. If you're using a Mac or other non-standard keyboard, look up the equivalent of the PrintScrn button for your keyboard on the internet if you don't have one. How would I know where it is? :p ;)

After you've gotten that cap into Photoshop, go back to QuickTime, hit the Right Arrow button, screencap the next frame, and copy that into the same file you put the other screenshot in. It's important that it's the same file, not a different one. It makes life so much easier that way.
Another important note: Do not, under ANY circumstances, move, re-size, shut down and restart or otherwise mess with the QuickTime browser. You'll be doing a mass cropping of your clip later on, and if any of the caps have the player in a different place, it will throw the whole thing off. Trust me on this one. You don't even have to understand why moving it is a bad thing, only THAT IT IS.

So...continue repeating the process. Again. And again. And again. If your computer is old and antiquated like mine, it may start giving you duplicate caps instead of one every frame. When, not if, that happens to me, I usually wait a few seconds and then madly bang on the PrintScrn button and it usually goes through. If your computer quits giving screencaps all together, you may need to restart your system...that usually works.

Let's fast-forward a few millennium until we are all DONE capping. Mine took forever...I ended up having around 70 frames to cap. I sincerely hope the clip you chose was not that long.
Anyway. Let's mass crop! *buwahahahaha*

Zoom into your mass-frame file and crop out the actual image from all the surrounding guck. Then crop it.

And, voila! You have a cropped image! :D See how I had the top layer "un-eyed", or invisible? That was so you could see Lucy's face for this demonstration, rather than a black screen. I'm all about aesthetics here, folks.

Now, before we teleport the file over to ImageReady for animation, we need to re-side this thing since it would just slow down the computer, and we weren't planning on having a 460x300 animation anyway. Or, were we? Never mind.

Go to Image > Image Size...

...and choose a reasonable size for an animated gif. I choose 200x82. Then choose "Ok".

See? All nice and small! Also notice Lucy. So much better than a black box, right? ;)

But, all good things must come to an end. To prepare your clip for ImageReady, make sure all your layers are in order and visible. That means you, little black rectangle. No more Lucy. *sniff* Now, mash that cute little button at the bottom of your PS toolbar, and off to ImageReady we go!

Now comes the long and arduous process that constitutes an animated gif. Since I'm incredibly lazy, I won't re-post the whole thing here...you can find detailed instructions over at my Straight to IR tutorial. Because technically, you *did* go straight to IR. You just um, capped by hand. *cringe*

Either way, you're all finished! Doesn't it look lovely? :D Just waiting to be turned into a lovely avatar or whatever.

Now, as far as YOU go...now that you're finished with this, you're going to want to make an appointment with a therapist to try and undo all the physical damage this tutorial has wrecked on your health. Your back, shoulders and wrists will never be the same again. Hey, don't say I didn't warn you!

Enjoy! Or not...;)