My all-time favourite anime is probably Moyashimon. It's cute, funny, and taught me everything I know about fermentation and I remember microbe names easily now.
Eureka seveN and Simoun are pretty high up the list, too. E7 was just amazing--the plot, the characters, everything worked together beautifully. Yeah, the Anemone/Dominic thing was a bit of a cop out but it was so cute.
This season I'm watching Star Driver, Togainu no Chi, Panty & Stocking, and OreImo. Star Driver is great, but the recycled animation is getting annoying. Fish Girl's song, too. It's a beautiful song, but do we really have to hear it every single time they enter Zero Time? I'm watching Togainu no Chi because I have some of the figures and I feel like watching it will "justify" the cost. That and TnC is one of the few yaoi series I like. I have a love/hate relationship with PSG. When it's good, it's great and when it's mediocre, it's horrible. It's more often great than horrible, though, so I'm okay with that. OreImo is...I neither like it nor dislike it. I do like that it's less "I want my hot sister" and more "Yay, I'm being treated like a big brother again!" if that makes any sense.