V model is used the most. Because with this model,
verification and validation processes progress simultaneously.

Hi 
Most of the companies use V model verification and
validation processes progress simultaneously, but it depends
on the company and the project they are dealing with.
sometimes they go for waterfall model. i.e. first they
design then develop then test etc.there are also models like
spiral model,fish model.....which they can opt for .

Now a days most of the companies are following/Using V-
Model as we can do the development and testing actions at a 
time to get bring quality software build.

regards
SoMu