As stated, good quality lined/pre-lubed derailleur housing and stainless steel cables from Shimano or Jagwire will ensure decent shifting performance. As for mechanical brakes, the Yokozuna Reaction or Ripcord housing is a must on a good bike, especially if you have disc brakes - there is a very noticeable improvement in brake performance (And don't forget the steel tubes in SRAM's Full Metal Jacket brake kit for discs). One thing that's seldom mentioned but is essential, is the need to always use high quality machined steel, aluminum, or brass endcaps.

Keep in mind that good shifting and braking depends on all the parts of the systems being carefully sized/installed/routed and of the highest quality - including stiff brake handles, short throw shifters, brake pads, tires, rim surface and true, cables, housing, endcaps, etc - and keeping everything clean and adjusted.