Lobby shooting spree, the gatling (sp?) gun on the side of the helicopter, the helicopter explosion and the part at the end were Neo bows out the walls are all impressive.
The dream sequence where the plane flies apart and the buildings blowing up at the end are great.
I'd add "Vertical Limit" to this list. Some awesome SHARP explosions (you can almost feel the shock wave) and avalanche effects are there for the enjoying.
I have the DTS demo disc 3 & 4 and demo my system a lot with them. I have more "do it again" requests for the scene in "Daylight" with the explosions in the tunnel. Then SPR, tank scene at the last. The scene in Predator when JV sets off that gatling gun is just astounding....