There are many different scales of Gundam from 1/35 to the most popular 1/100 or 1/144 (also has some other smaller scale for space ships.)
These 2 shown in picture are the most famous bad guys in the side story of the first series. I like them a lot for their military look (also look like the storm-troopers in Star Wars). For example, the green one above is holding a Panzerfaust.
If you are interested in these, please feel free to check my web for more information and pictures.