The simple answer is...
ILS 12.75 - Universal Laser Systems
Not the strongest, but it's pretty strong.
The secret service has it, and you can't
I faintly remember reading about one in michigan that wasn't pulsed in the megawatt range :eg:
Can't find the article now...
EDIT: ^^ ahaha, I missed him saying "pointer".
Well, www.rayfoss.com
That will be a nice burning pointer
EDITEDIT: Are you asking this for information, or are you looking to buy something? IF you're looking to buy something and this would be your first higher powered laser, DO NOT buy what I linked you to.
If 200mw burns a match.. then 3-5w would leave marks on walls..Honestly, I would GIVE UP on your dream of having a handheld burn messages or images into a wall, It is just not gonna happen for any reasonable amount of money and plus that kind of power is extremely dangerous. If your are looking to write on walls with a laser pointer then I suggest that you buy a can of glow in the dark paint from a hobby store and paint a wall with it. Then use a low powered (5mw) 405 laser to write messages on the paint once it has dried. Cheap. Easy. Safe.
- Matt
Look: Blu-Ray UV Laser Drawings on Glow in the Dark paint - YouTube