You can make infinite mana, infinite ETB triggers, LTB triggers, life, death triggers or +1/+1 counters on lots and lots of creatures, most of which are very unfair
For example, if a creature would normally enter the battlefield with three +1/+1 counters on it, it will enter with six +1/+1 counters on it
It pairs well with Plumb the Forbidden since you can use Sedgemoor Witchs Magecraft ability to draw cards and gain a bunch of life
Breach deck building has demonstrated a lot of unexplored territory as well, which has captured my attention
I am going to list some non-engine cards now so you can just pick out whichever non-engine you personally find the most fitting
One thing is for certain: every player should build at least one Exodia deck and show everyone watching that Yugis Grandpas deck has no weak cards.