Yeah, JMS himself stated that PPG's have no stun setting. You can use them to clobber your opponent over the head though... that would stun him I'd guess... :wink:
However, there obviously are guns that can stun an opponent - just look at Tu'Pari and what he did to G'Kar. And I'm pretty sure there will be high-tech versions of the tranq rifle used today to make wild animals sleep peacefully without doing any permanent harm.
Just no "CanDoItAll-pistol". (OK, so the Vorlons will probably have 'em, as they are permitted any wierd and nifty tech goodies as part of their "ancient" status, but even the Minbari Sha'ann has no stun setting, otherwise the conversation in "Lines of Communication" would have mentioned that firing option...)