I, like others, really recommend my little dashie.
Some of My other favorites that I would higly recommend are: Tiny Wings, Her Majesty Walks, and Bubbles (warning those are sad stories)...oh and A Rose Reverie (very good if you like plot twists)
I know you said you don't like grimdark fics, but if you want to try the ultimate one I'd recommend "A Fun Day!"...it's 10x worse than cupcakes but extremely funny if you have the right sense of humor.
Here are the links:
Tiny Wings: http://www.fimfiction.net/story/23865/Tiny-Wings
Her Majesty Walks: http://www.fimfiction.net/story/24844/1/Her-Majesty-Walks/Life
Bubbles: https://docs.google.com/document/d/1RgkrBTryVCfmAARA5ZCMTY4nTa2ta2-mhmdpxvipEoA/edit?hl=en&pli=1#
A Rose Reverie: http://www.fimfiction.net/story/10883/A-Rose-Reverie
A Fun Day: Can't post the link because I'd probably get in trouble, but you can find it on http://www.fimfiction.net/ by searching.
I know what it's like to struggle with fanfics, so I hope this helps.