It seems like five-point and 8-point circles should be viable. The two-point is the most difficult to explain in terms of a nine-point circle. If you look at the limit as the vertex angle of an isosceles triangle approaches 180 degrees, you end up with a circle of infinite radius, with 5 points converging to lie on a straight line. This can't exist on a circle, but if you also take the limit as the side lengths approach 0, they converge to a single point. The other three points lie an infinite distance away, along three parallel lines, which, again, can converge to a single point for zero side lengths. I suppose this can be seen as the two-point circle, but it is somewhat more abstract than the others.
Note: taking the limit as the base angles of an isosceles triangle approach 90 degrees and as the length of the base approaches 0 and the lengths of the other two sides approach infinity gives an identical result.