US 15, Gettysburg, PA. From the MD state line to PA 94. Completed as a super-2 with full interchanges in 1963, the full buildout was completed, much as originally envisioned, in 1989.
US 15, Buttonwood, PA. From PA 184 to the Sebring interchange. Completed as a super-2 in 1976, the full buildout was completed, much as originally envisioned, in 1998.
US 15, Mansfield, PA. Mansfield Bypass, from PA 660 to PA 287. Completed as a super-2 in 1987, the full buildout was completed, much as originally envisioned, in 2003.
The astute (and even not-so-astute) reader will detect a certain theme here. PennDOT (and it's predeceasor, the PA Dept of Highways) had a fondness for initially constructing super-2s and building them out later.
One project not this category is I-476, through the western suburbs of the Philadelphia area. Known locally as The Blue Route (the name being derived from the color of the selected alternate's line on planning maps released to the public), parts of it were constructed long before the entire facility was completed. One section, from approximately Darby Rd. to Sproul Rd., sat unused and unconnected to any interchange for 21 years. Locals used to fly their model airplanes from it. This segment was shy of PA 3 at its southern end and US 30 at its northern end. (The highway didn't reach these routes and interchanges were not built.) This unused, unconnected section was built in 1970 and finally opened to traffic in 1991 when the entire freeway was completed, interchanges and all.
(Thanks to PAHighways for providing specific dates.)