This is the Evangelion Pallet Rifle, the rifle is a mixture of the different iterations seen throughout the series, and takes a lot of inspiration from the scale figures. This model is a human sized replica, measuring 30.7 inches long, the same length the Steyr ACR is, which is believed to be a heavy inspiration from this iconic weapon. The model has a long rod piece that can be printed twice for support. Many of the pieces can be easily lined up using the built in peg system, but will require super glue to be held together firmly.
Have fun, and happy printing!