1st video ( with slash )

it can be achieved by using a delay esp analog delay. feedback almost 100 % and played with the time knob.

2nd video

he use a keyboard and later play with the pitch slidder..can also achieve by using whammy pedal

megalomaniac ? i think it's also analog delay but being mash up with other effect ( maybe studio )..kinda like through his gankulator..

there's only 1 band who did everything with pedal : rage against the machine