Making a gun which creates portals isn't impossible at all. Heck quite a few people have done so, such as Allan.
a portal maker, not a teleport gun
yeah allans gun is awsome but it teleports you to the projectile hit vector
i want one that can create 2 portals at atime linked by a tag/event so when you go in the 1st portal it takes you to the 2nd an the 2nd takes you to the 1st, then after you shoot a 3rd portal they disappear so you can make another 2 portals
or maybe a better way to explain is that
it should spawn a tele1 wherever it hits, an a tele2 wherever you shoot next so you can walk in where you first shot, then come out where ever you shot next
like you can even stick decorations such as crates in the portal
this youtube video shows a better example
http://www.youtube.com/watch?v=ZEGRAORCNYA