Aayatul Kursi After The Prayer
Abu Umaamah (may Allaah be pleased with him) said: the Prophet (sallahAllaahu alayhi wasallam) said:
“Whoever reads Aayatul Kursi after every obligatory prayer; nothing prevents him from entering Paradise except death.” 
Meaning if death was to come to him at that moment then he is going to Paradise inshaAllaah.
And since none of us knows when his death is coming, then it is upon us to be diligent in preserving this great deed.
1.Saheeh al-Jam’i: 6464