And when you leave the service, your DD-214 and medical records.
Even though I'm still "in," I already have two DD-214s (this is unusual but not extraordinary). I have one for going to OCS and one for when I switched from active to FTS (that second one was something of a paperwork drill that didn't make sense to me; I pressed my personal "yes sir/I believe" button).
I was
kinda surprised how it simple it works to get a DD-214. At PSD a GS-xx (probably used to be a PS3 or PSSN) drafts it while you wait, his/her supervisor QA's the document, and badda-bing there is a hugely important piece of paper in your hand with the past several years of your service, bye-bye take care now and thank you very much. And if you thought it was important to
read the fine print before you sign the paperwork on your original contract to join up way back when...
@stickygdm, concur on the SERE, FITREPs, etc.
PS- Arrrrrr, look at the date on ye ol' calendar today. Shiver me timbers!