(Totally oblivious to the comments above.)
Well, here's my list:
This anime was really short, but the plot was amazing. I thought the ending was really strong, because it really mixes pity with vengeance. Most animes fail to get a perfect emotional mix, but Elfen Lied did an outstanding job.
Relaxing animes are great in my opinion. Cromartie Highschool was a gem in the gag and relaxing anime genre. Whenever I watched it, all my worries were replaced with laughs and happiness.
I don't know if it's just me, but I love Eyeshield 21. It is an excellent anime, and watching it only makes me want to watch more.
The manga was amazing, and the anime was great. I can see why this influenced so many mangakas, and why it is so loved.
I really don't see this as a ground-breaking anime, but it's a really calm and relaxing anime. The only bad thing about Ranma is that once you finish it, you crave more. We really need more animes like Ranma.