GP guns are a waste of resources. GP should be used for skills and making CR guns unbreakable.
One of the things this means is that the APS is the only machine pistol you’re going to get for quite some time. I find it quite a dependable sidearm, especially on a sniper class.
Kedr, on paper, looks like a weak weapon, but it’s so dirt cheap that it’s probably worth getting just to have it. Making it unbreakable probably costs next to nothing too.
One I haven’t heard yet is the KAC PDW. Treating it like it’s a burst fire weapon has given me good results. In addition, the next two assault rifles, at least by the numbers, aren’t all that much better.
And if you have 10 extra Kreds floating around leftover from another purchase (otherwise, probably not worth it), picking up 30 extra GP unlocks the Glock 17 DEVGRU, which is currently my favorite sidearm.