So, of course, I have some recs for you (even though it is very, very hard to choose and I really suggest you just go read everything in her journal):
The Most Wonderful Time of the Year -- (Sam/Dean, NC-17) -- How teenage Sam and Dean spend one Christmas. When I think of wee!cest, this always is one of the first stories that pops into my mind. The scene in the hotel room is one of my all-time faves.
Pour Some Syrup on Me -- (Sam/Dean, NC-17) -- Pre-series Sam and Dean, pancake syrup, a knife, the Impala, some sweetness, some angst. What more do you need?
The Party of Almost Was -- (Sam/Dean, NC-17) -- Sam knows what he wants from Dean, Dean is less sure. This story just WRECKS me. I just pulled up the link and I got tears in my eyes. There's some powerful stuff here. There also are more parts, so if you like it, keep reading.
A Fire of Unknown Origin -- (Sam/Dean, NC-17) -- Sam has a pain kink and he goes out of his way to get Dean to play. There also are more parts (both before and after this one, though you can read this one as stand-alone too), so if you like it, keep reading.
Man, choosing among her stories was painful! I really could just list every single thing merepersiflage has ever written. So, if by some odd chance, you haven't read her stuff, I really urge you to call in sick and just spend the day catching up on ALL of it.