My favourite is the self-replicating solar factory (Ultimate with GT slightly nerfed - no bronze nerf, no solar nerf, no macerator nerf).
Start off with a small system using frames (a frame space-ship containg a solar panel, a batbox, a mining turtle, a mining well and an electrical engine) to mine and a processing AE facility that macerates coal and all the stuff and a simple system that puts wire and the panel using frames+deployers (powering the whole facility).
The frame-ship mines a line (you can also use a sytem I created using BC gates to check wheter it is charged or not and guarantee there will always be a full redstone energy cell) and gives all of its items to the AE sytem.
The AE sytem sorts it and makes every single thing (note: it also has a rubber farm from MFR using MFR trees into an extractor/rubber into a furnace) of the solar panels (it's powered by a small system that is the simple power loop of Magmatic Engine+Magma Crucible and Igneous Extruder).
The solar are put in a placing system that powers the whole line of AE.
Once you get to a point you are producing more energy than consuming, BOOM POWER LOOP!