Nate had been asking Sarah some specifics on what to take on his mission.  Though this list isn't comprehensive, Sarah has shared some details on what has worked for her:

small english BofM (the mini one)
recent, fun family pictures (to show inv. and companions)
weird, american snacks you know you'll miss
1 big camera memory card (32 GB)
flashdrives (to back up pictures)
clothes that actually show personality (don't just take the boring and practical)
nicer clothes just for mission conferences
extra garments to pull out after the halfway mark
small hymn book
small PMG (laminate the cover)
jump rope (easiest way to exercise)
twistables for scripture marking
a binder of favorite/good missionary conference talks
sturdy, water proof watch (doesn't need to be expensive)
towel (just don't get one really thick, the ones I bought were fine) 
1 pillow/1 fitted sheet (that's all you'll need)
cheap, LOUD alarm clock that uses battery
bball shorts (p-day clothes double as pj's)
*you don't need a ton of bug spray like it says in you call letter
shoes-1 nice pair
flashdrive of good/not boring church music (depends of mission president what music is allowed)
debt card/wallet
pair of normal/pday shoes
good pens (you write allll the time)
study journalS
*leave your suitcases a little empty, you WILL get lots on your mission
*don't worry too much, you can probably just buy it there
*the MTC will give you a dictionary, scriptures in your language, language study books, and a big PMG, a filtered water bottle