optimize blenderswap models for unity (mobile use) i like some of the models on blender swap but the issue most of them have the models as separate meshes and materials therefore it will be a lot of overhead on mobile performance, is there an easy way to open the file in blender and make all the meshes as one object with one material ,  and if there is also an easy way to reduce number of verts it will a lot of help?
As Duarte pointed out, there are no "easy" ways to optimize models for games - especially mobile games - efficiency is everything for mobile.  Most game models are built with a "budget" in mind, and every component of them - from the geometry to the textures to the rig and animations (if it has them) need to be carefully considered with that budget and  overall optimization in mind.  In my experience as a modeler (for games) high-resolution models can present a usable framework to build a low-poly version around and then maps and normals can be extracted - but it will be a very rare object that you will be able to use straight away.