Simple Screen Recorder

Screen Castify is a simple screen record add-on to record your screen. It has following features.

• You can select options to record your desktop, browser or a particular tab. 
• Screen resolution can be adjustable
• We can start/stop/pause/resume recording using shortcuts and shortcuts and configurable. 
• It generates webm which can be viewed in chrome/firefox.(You don't need additional video player to view the video). 

Here is th addon 

https://chrome.google.com/webstore/detail/screencastify-screen-vide/mmeijimgabbpbgpdklnllpncmdofkcpn?hl=en

Cam Studio is able to record all your audio-video activity on your screen  and generates most popular avi format. You can include images, texts and callouts. It also includes the customization. It is a portable(<3MB) software and most importantly freeeware.