Mallard near anyone who has grown up here has used either a 270win, 308win or 3006 at one time or another. Well actually I should add the old favorites as well to that list 3030 and 303 british. 300 wm and 7mm rem mags are very popular choices, as is the 338wm for those who hunt elk and larger with regularity. As far as scopes I don't see the need for anything larger than 10x for biggame hunting. Personally if I were assembling a 3 CF cabinet it would look like this:
.257 cal (2506AI or 257 wby) Varmit to deer
.284 cal (7mm Rem Mag) deer to moose
.375 cal (375 H&H Mag) anything that walks