If you're a gun owner moving into California, it would be advisable for you to read through the LegalCalifornia section. There are a few states with more restrictive gun laws, in which case you will be happy. But for the most part, you will have to sell or store some of your collection outside of California before moving in.
I will also state that this is by no means a complete list, only a list of things which I remember.
Certain Martial Arts Weapons
Although this is not gun related, it is important to read through the California Penal Code to ensure that you don't own any prohibited martial arts weapons. Nunchaku, throwing stars, and many other novelty weapons are a felony to simply possess in California.
Gun Accessories To Dispose Of
Multi-burst Trigger Activators: Although a largely useless novelty, the "gat" or "hellfire" trigger activators are illegal to possess in California. Not just to have installed on a weapon, but to own at all.
Tracer, APIT, or incendiary ammo or projectiles: Due to the fire risk, each of these loaded rounds or projectiles is a FELONY to possess!
Large Capacity Magazines
It is not necessary to dispose of your large capacity magazines when moving into the state However, it is necessary to disassemble them. You may not reassemble them within the state, but there's no law against having all the parts for when you move back out or the law changes. See LegalCaliforniaMagazines for more details.
If you own any of the weapons on California's various assault weapon lists, you may not bring them into California unless you happen to be active-duty military (see LegalCaliforniaMilitaryAWP to see if this applies).
Any unlisted weapons must be in compliance with the assault weapon code, which you will find in the various sub-sections of LegalCalifornia.
First off, all handguns you bring into California must be registered with the Department of Justice! You must fill out and send in a New Resident Handgun Ownership Report. It will cost you $19 per handgun, and it is mandatory, not voluntary. It is not necessary to ensure that your handguns are on California's drop-test list; that only applies to new purchases made within the state. It does not apply to weapons you already own, unlike the assault weapon bans. You should take this time to look through the drop-test roster and see if there are any handguns you really want to have, that aren't on it. If you see any, you should buy them before you enter California. This includes Mateba auto-revolvers, various MAC-10 styled handguns, and H&K squeeze-cocking pistols.
It is also noteworthy that unlisted handguns within California may be transferred via a private party transaction (done via a licensed dealer, but face to face with the other party), but not sold by the dealer. You should not rely on finding off-list handguns available for PPT, because it will generally be much more expensive due to the limited supply. Some folks have been known to "stock up" before moving into California, in order to take advantage of this.
Yes, California has a law against flamethrowers. So, if you happen to own one of the Chinese milsurp flamethrowers that was on the market a while back, you can't bring it into California.
-- SeanNewton - 01 Nov 2007