I second Gintama and Fullmetal Alchemist Brotherhood. They are top rated and well loved anime for many reasons. Great character development, comedic timing, and serious moments that really have you cheering for the characters by the time it's all over. I wish I could experience watching these two for the first time again. I can watch them again and again too!
Honorable mentions to Code Geass and Made in Abyss. They each have their wow/shock factor that, for me, had the greatest impact on my first watch. When I rewatched them, I know what is about to happen, so I am mentally prepared this time lol.