I've ordered everything on the list 'cept the pistol grip. everything else is fine. Just make sure there are no dummy bullets in/on the mag. (hi-cap mp5 for eg.)
Grey area items are:
silencers (with no trades are hit and miss... mostely miss) some grenade/shower shells (depends on how realistic they look).
No-no's are obvious:
guns (actually it's the receivers and metal bodies. Barrels, stocks, handguards and sights are fine)
203 trigger styled launchers (button type are fine.. at least for me.)