Helicopter are made down-to-a-weight. When the "assembler" (better term than manufacturer in most cases) buys bits he has a lot of boxes to tick. Nobody seems to give a s**t about whether they actually work or not.
I'm going to begin a list and hope someone else will finish it off:
SeaKing 1 - Hydraulic Screen Wipers that failed every time after 10 mins use
Most Types - A PA system that can only be heard if the engines are NOT running.
Seats we have done to death but always deserve a mention - particularly the S61 "killers" otherwise known for their contribution to the profits of those that make haemerrhoid suppositories.
S76 Brakes - Minimalist or what!
S61 "Purge meter" or screen wash - the guy who put that there had a hell of a sense of humour
Luggage bays - read handbag container
Bo 105 Rotor brake - one way of exercising your right arm providing you don't need to stop the rotor in winds above 40 kts
Bo 105 Stab System - rearrange the three green lights in any order you like and see if you can tell if the sytem is in or out.
Go on - vent your wrath, maybe the odd designer or two is reading this thread.
G