Update 10/22/2014: Seth Johnson has improved the Ubuntu PPA so that only the Silentcast PPA is required. (Previously, 3 PPA's were needed.)
Update 10/13/2014: Version 2.0 released. Added options to ...
My Experience is:
1st Place: as Sterex suggested, Open Broadcast Studio
OBS really provides a whole lot of flexibility for creating complex layouts which you can change on the fly while recording.
Since I don't prefer any of the other solutions since they don't have the specific features I want, I made my own (currently command-line only) program specifically for quickly capturing .gifs and ....
I've used GTK RecordMyDesktop before and was pleased with the result (but note that I have used only once for really simple stuff).
[X] Must be gratis
[X] Must work for Ubuntu 12.04
[?] Would be cool ...
You can use Screencast-O-Matic:
Straightforward to use (demo)
Most features are free but you need a pro account if you want to record videos longer than 15 minutes or control ...
You can use FFmpeg:
Free and open-source
Runs on Windows, Mac and Linux
Allows to split video into pictures: e.g. ffmpeg -i input.mov -r 0.25 output_%04d.png to get a picture every four seconds.
Any program (Windows Sound Recorder, Sound booth, audacity etc) that records audio can record sound from windows, you just need to know how to set windows up.
You are not really looking for another ...
I recommend ScreenToGif. While it has some downsides it's a free tool which is extremely easy to use.
It's free without a watermark
Easy to install and use
It now can capture the whole screen ...
Please see the authors update at the bottom
Spotlight Recorder Utility
I realize this is an older questions - but I have had ...
VLC media player
Can capture the screen
Can capture a webcam
Can record audio (in conjunction with one video input if desired)
I have already posted a manual on how to do the things mentioned above ...
The free version has all the features (and even more) you want:
no watermark for WebM (*)
runs on Windows
selectable portion of screen