The most obvious:
intercooler, manifold, downpipe, and lets not forget the turbo itself.
Then you have the wastegate if the turbo isn't internally wastegated, blow-off valve, or a blow-through setup, the intercooler pipes on the hot side (right after the turbo, before intercooler), the intercooler cold pipes (after intercooler, before throttle body), oil return line, oil feed line, oil bung for oil pan, T-fitting to feed off the oil.
And finally, you have all the miscellaneous connectors, couplings, adapters, nuts, bolts, gaskets, etc etc.