Recognize the original poster seemed to be looking for some sort of para-military like pistol calibre carbine, though several folks have suggested the handy little Marlin and Winchester lever guns.
I'd like to chip in my ha'penny's worth for the handy little saddle carbines. It's also hard to beat one of the pre-lawyer safety BROWNING iterations of the Winchester 92 in 357 or 44. Shouldn't need to repeat Cooper's comments on the virtues of the PC urban assault rifle, but the little Browning's are so superior in quality and accuracy to anything else on the market, that they are certainly worth considering if one can live with the Japanese production of an American classic.
Marlin 1894's and Winchester 94's in pistol calibres are certainly functional. The Marlin probably has the edge for fast and extensive shooting such as in CAS plus it is easier to strip and clean than the Winchesters. Still, I've seen few folks who handle the little 92's that don't fall in love with them. I have original 92's rechambered to 44 Mag to handle any of the 44 cartridges, but the little Japanese Browning in 357 was just so handy and pretty, I couldn't resist picking up one not too long ago since the price was right because someone had drilled and tapped it for poor quality tang sight. Lovely, accurate, fast handling little carbine. Zero perceived recoil and muzzle jump----Now if I could just find a serious reason for a carbine in 357......but then what sort of fool demands a REAL REASON for picking up a new weapon....