My fav. pokemon changes from time to time, as new ones are created and stuff, but my all time favorite trio would be Pichu, Pikachu, and Raichu. I love electric pokemon, and Pichu's just adorable, everyone's got to love Pikachu, and Raichu because its still adorable as the third evolution, which is when most pokemon lose their utter cuteness, if not by the second evolution, it's pretty useful (on my team at least) and it completes the trio.
My favorite legendary would have to be the Latias and Latios duo, they're awesome! Don't have much more to say, Latios is pretty darn cool, and Latias is so loveable and cute (don't you agree?)