I have a Surefire X400 that I am looking to modify.  I have had the selector toggle switch that goes from  OFF -> LIGHT -> LIGHT/LASER -> LASER -> OFF get bumped and change modes on me more than once, which is obviously unacceptable.  Does anyone have any advice to help with this issue?  I use the light only setting 95% of the time and the light  with laser the other 5% of the time.  I would be okay with a fix that keeps the device in either of those two modes, as long as I have light when I need it basically, the laser is not really important to me.   I have considered trading it out with someone who has an X300, however I have 2 Raven holsters setup for it when it's on my Glock and don't want to give that up.  I also spray painted it, so it is likely not going to be very appealing to most.  

Any help will be greatly appreciated!

If the selector is loose, send it back to Surefire.  They will fix it.  I had an issues with my first X400 and they sent me a new one.  The second had a stiffer selector.

I have this same issue. I usually leave it on Laser/Light all the time. What I'm considering is cutting the selector switch so it is much harder to bump. I just haven't gotten the balls to do it yet. I'm worried there is an unforeseen issue in cutting the switch lever. I wish Surefire had put a set screw in the selector. Even told them so at SHOT.

I see no reason to be tinkering with Surefire s*** when you can send it in to get it fixed the right way. Don't risk it and get it done right the first time.

Nothing is wrong with it per se, so there isn't anything that Surefire can do to "fix" it.  It is more of an issue of the design, and I am looking for DIY fixes for it.  I am thinking of super gluing two small pieces of plastic on either side of the selector preventing it from being bumped to either OFF position, or to laser only, keeping it in a mode with white light no matter what happens. I'll post pics if i ever get around to doing to.