Might as well bring up something that hasn't been mentioned here or is very unlikely going to be brought up.
Gunpla, or gundam plastic model kits. Unlike your usual kits these don't have to glue together and paint (unless you want to give your mecha a nice finish). Quick easy to build, and excellent results even if you have hardly any experience in the field of modelling. All you need is nippers, a craft knife and patience. They're also in most cases very solid, they won't be falling apart but if you are really concerned about that get hobby cement (which costs about £3-5) it'll will fix that. Oh and did I mention they're very pose able (although again it varies from kit to kit).
I own about 5 kits, out of all of them my personal favorite is the rg freedom gundam. It has folding wings that spread out, railguns, armour that shifts independently up and down depending on how you pose the legs or arm, and two beam sabers that form into one.