Probably the easiest program to create 3D models in is Google's Sketchup (its free too!). The program is incredibly user friendly, if you can understand MS Paint, then your off to a good start, there are some built in tutorials, if you watch 2 or 3 of them, you'll be set to start creating things. It has a huge online collection of 3D models, that is completely searchable. Personally, I've never used it to create models for a game before, but there are tutorials online on how to convert from Sketchup to Blender.
Anyways, I highly recommend checking out Sketchup's 3D Warehouse with all the models that people have shared, it would probably be a fantastic resource for premade templates of just about every item known to man.