I always find this difficult to answer because only you know your skill level. Some objects have a lot of cuts or curved surfaces, which is a bit more difficult. But I had to think of Jonathan’s post right at the beginning, so maybe that appeals to you
https://blog.cgcookie.com/top-3-things-every-beginner-blender-artist-should-model/?playlist=fek8wv
I would suggest you take something from your surroundings, then you can take a close look at it and hold it in your hand. This makes things a lot easier. For hard surface models, you can start with a keyboard or tools, pliers, a cordless screwdriver or something similar.
Or just have a look at the Weekly Challenges and choose something from there. Just go to Commuinty at the top, set the filter to “CGC Modeling Challenges” and have a look. I’ll try to link it below
https://cgcookie.com/community?sort_category=254
