Rural Emergency Medicine Simulation Training and Resource - British Columbia
It is impossible to cover all possible ECG findings one would come across in an ER.
However there are several that you
really don't want to miss.

The Power Point below covers some of the
more potentially deadly ECGs
it would be best to be familiar with.
These are some videos on aspects of ECG and arrhythmias.

The link  below is the article by Litman et al (2014)on the diagnosis and treatment of PEA referred to by Dr. Mattu in the video above on "Resuscitation 2015"

Pacemakers and ICD - how to deactivate.
In dying patients, a pacemaker will not 'keep someone alive'. The heart muscle will not respond to the electrical impulse. ICD will usually not work as the the rhythm of a naturally dying patient is usually not shockable. However, the ICD can be deactivated by a magnet. 
The link below explains magnets and pacemakers/ICDs.