Honestly, I wouldn't mind catching any shiny, but I can't tell you how many I've walked by them and accidentally click the x button on instinct.
ALL THE SHINIES! Jokes aside, I would actually scream (in joy) if I got these: - Any Shiny Legendary - Shiny Beldum (I really like Shiny Metagross) - Shiny Snivy - Shiny Egg - Shiny Vivillon (any Vivillon will do)
Spiritomb and Charmander, maybe one day. Also won't say no to bacon bird Yveltal if I come across one.
Ponyta, Vulpix (already mentioned), Swablu, Duskull, Shinx, Buneary, Roggenrola, and Carbink (or their evolutions) are all among my favorite shinies. But then again, I already have my Gardevoir, so what more could I want?