ump slaps, 74u is good for its price, scar is mostly used and good, m16a4 is good if you're tap firing from distances with a acog or some sort, whatever your personal preference is
I have not tried many guns, but usually when I'm defending I like to use the SPAS 12. From the last ~20 raid attempts we've had (I usually play with 1-2 other friends), only two succeeded, and the raiders had grenades and/or door explosives + very high level assault rifles.