Our SM gives the youth a personal gift.  When it was my sons getting their Eagle it was a Savings Bond, I believe it still is.  They still have not cashed them in, and it was over 15 years ago that they earned them.  However, they gave the SM at their ECOH a gift. It was a statue of an owl looking owver two young in the nest.  Very reflective since it is well known in our troop that the SM is a WB owl....He still has it, and it sits proudly on his mantle. My sons were # 4 and #5 Eagles in the Troop and we have just had the BOR for #50, all under the same SM.  
The Troop provides the presentation kit, neckerchief and a binder of congratulatory letters.  If the youth chooses not to have a COH, then he received the binder of letters.