I'm going to have to go with a high pressure 4-4 scheme. I think that gives you more flexibility than even the 4-2-5. I personally think it's easier to take your most athletic OLB and drop him back to safety for a cover 2 look than having a safety roll down and play a designated linebacker position. Having 8 in the box in high school I think is paramount as 90% of the juggernauts are super run heavy. My favorite 4-4 schemes are gap controlled like mentioned before with Wapokoneta. I personally prefer the "over front" where the 3 technique is to the offenses strength and has the B gap, and the nose is in the 1 technique away taking the A gap. That 1 technique player MUST command a double team between the center and guard. Now, my favorite alignment is with the strong side DE, if there is a Tight End, he will line up inside the TE's shoulder in a 7 technique. Most teams put that DE outside the TE in a 9 technique for contain, or put him on the outside shoulder of the OT to play C gap. I like the 7 technique because it forces contact on the TE on every play, so free releases are hard in pass game. You also dictate who the TE blocks in the run game. You teach that 7 technique DE to make contact with TE every single play. This has to be your best D-lineman. It should also force a double team with the TE and OT on that strong-side DE. With this alignment, you have 2 D-linemen being double teamed... you are using 6 offensive players to block your 4. That leaves your LBs to run free and be studs. Then the fun starts when you start blitzing the H3LL out of your LBs, Safeties, Corners, etc. The offensive line breaks down very fast leading to smothering defense. You combine this with a few simple but effective coverages mixing in a couple of zone and man coverages. The last team I saw run this defense was LaSalle's last 2 years of winning state championships. Man, those boys were swarming all over the place.
A close second would be St. X 3-3 stack. It has been imitated by many and perfected by nobody but St. X. It is a thing of beauty to see the Bomber Defense when it is clicking.... it's very simple, but offenses can never seem to figure out how to attack their scheme, even though they've been running it for probably 20+ years.