I'd consider robots to be beyond the realm of what we could achieve in 10-20 years (at least believable, sentient ones), but lasers are not quite an impossibility.  It would more be like a focused wave of intensively uncomfortable heat though, probably used to keep citizens in line rather than actually<em>kill</em>anyone.  They're already working on such weapons for military use.  There are videos online last I checked, with test subjects being forcibly turned back because the heat became too much.  Not "spontaneously combust heat" though.  More like...  "Stimulates-pain-nerves-heat".  Guns would still be the weapon of choice.