what is the best graduation gift that I can give?

Okay........ so I have these friends and classmates and dorm mates who have been with me since 2011.... Literally lived with me.... and this coming December 12 is our graduation... after which we may part forever and never meet again.... what can I give as a memento???

Help badly needed!!!!!!!!!!!
They are really important people!!!!

And we lived with nuns without any contact with our families so it's very much like they're my family for almost 4 years plus we're really super close!