Greetings minecraft forums, neonstory this is a great post, listing ideas and commenting on eachothers this will be a great tool to create an incredible game truely from the fans, now i am going to list yours and other minecraft players ideas and my own ideas and comments on it all:
computer-great idea should require many advanced materials and difficulty in construction as it is a high tech item and would require an advanced society to "invent" ideas for usage: advanced menu-based controls for switches red stone wires to everything in your house:P
doorbell-actually with the newest minecraft has an item called the "noteblock" and with a button and wires you can have your very own invention: doorbell
lock- yes there could be locks and keys using iron ingots and other items like gold or sticks and for both sets of doors by altering the minecraft engine in heavy ways but for now this can be done simply with iron doors (vs wood) and buttons hidden in stone or wooden walls
a calculater simply isnt necessary considering the interface numbers all items for you and it is good for u to do ur own math
rock paper scissors... my suggestion would be
dice 
"lights out" i believe you are saying notch should create an electrical red stone wired switch activated lights? i agree 110%
tnt cannon- one word: hellyea! my idea for this would be to create a pattern incliuding obsidian and various redstone items to create the cannon, and the gun would be using expensize (needs tnt, gold, iron ingots whatever) to make a large ammount of bullets) and useful ammunition due to its improvement over the bow perhaps instant travel time, and lack of mobility as a debuff
tic tac toe- good idea but unimportant to my interests (lol)
(i touched on a lighting system earlier) good material ideas are glowstone redstone wires and buttons and switches
working minecart system-(using a computer to control distant rail switching and remote cart activation, or manual switching at the location of track-intersections, and redstone wires connecting it all) another item would be connecters for minecarts... allowing the engine to lead like it should be
(ignoring the infinite obsidian mine due to my personal beliefs in preservation of the survival aspect of minecraft)
fix double doors yes
A viedo moniter and video cameras should be used along with the computer idea and it would all come together with redstone wires and have a large limit of total items controled by the computer viewable on a moniter as a menue and can access camera video, minecart control, and control of the lights and doors and anything else electronic to be added)
spawner... i believe spawners should be found in ancient underground and surface ruins that should be added as a challange and for capturing the spawner you can place it anywhere to farm the mobs of recorces
Programable timer-YES the delayer/repeaters are very confusing and not very effective and timer should be added and perhaps included into the computers functions
water toggle-the current water control is very limited and this is manditory! there should be remote controllable doors for water blocks (1 block high only) and controllable by the same computer interface
giant clock... ill support a wall clock of sorts..
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mine...
