I think that the limits that you put on the 260 are directly related to the skill of the shooter, the accuracy potential of the rifle, and correctly matching the bullet to the intended target.

If you are a reloader, the 260 is a very useful varmint and non-dangerous game cartridge. If you are not a reloader, there aren't many 260 factory loads available and those that are available are (it appears to me) intended to shooting deer.

I've settled, for the most part, on the following bullets in my 260s:

95 grain VMax for varmints and small deer, anything under 125 lbs.
100 grain BT or Partition, medium game.
120 grain BT, medium game.
129 grain SpirePoint or SST, medium game.
140 grain Partition, medium and larger non-dangerous game.
140 grain AMax, punching paper.

If limited to 1 bullet for all purposes, I'd opt for the 140 grain Partition, however since I'm not, I shoot a lot of 100 grain BTs and 129 grain Hornadys.

Jeff