Best prayer is asr on Arafah
خَيْرُ الدُّعَاءِ دُعَاءُ يَوْمِ عَرَفَةَ
Khayru-d-du'a'i du'a'u yawmi 'Arafah.
"The best dua is the dua of the day of Arafah."
Narrated by Amr ibn Shu'ayb. Sunan at-Tirmidhi 3585
A short reflection
Whether you are standing on the plain of Arafat or behind a desk that day, the hours are charged differently. Spend them in supplication.