1. No Avengers party scene.
Maria Hill was in the party scene. Here's a description of the scene: The Avengers are betting about who could lift Mjolnir. Tony tries and can't do it. Then he tries with an armored arm. Then he and Rhodey both try with armored arms. Bruce tries and Maria Hill jumps because they're afraid he'll Hulk out. Clint tries. Finally, Steve tries and barely nudges it. Thor says they're all not worthy. Enter Ultron, saying humanity is not worthy.
2. The ending.
Tony awakens from a vision/being knocked out/dream/robotrip in a landscape of rubble. All of the Avengers are "dead". Tony first sees Steve's shield FUBAR, then the ending shot is DEAD STEVE.
3. Bruce naked and alone in a snowy forest