Is there a All-In-One Bike that I can use for several types of riding? Is there a bike, which can be used for several types of riding? By this, I am referring to commutes, tours, cross country, off-road mountain biking, trailing especially.

The bike should contain the major quality of several specifically designed bikes. By this I mean the following:


Road Bikes: Lightweight, speed, ergonomic
Downhill MTBs: Rigid Frame, High performance suspension and Tires
Cross Country: Comfortable (on Long tours)


For me, I have an habit of using a MTB for most of all the activities I mentioned above and most of time, this is not an comfortable experience over long run.

So, the question is simple Is there a bike, which contains all the qualities in one?
In general you can get an very good all-around road bike, or a very good all-around mountain bike.  To get a single bike for everything there will always be trade-offs in areas like weight/durability; speed/traction; etc.

That said - many people own one bike and use it for everything.  If I had to drop to one bike I would buy a 29"-wheel based front suspension mountain bike with the following:


suspension front fork with lockout
disk brakes 
rack and fender mounts (and a rack and fenders)
a spare wheelset


In my mind the spare wheelset is key - that way you can run a high pressure slick on one set, and then switch to a knobbie without the hassle of swapping out the tires on each wheel.