For big game, my general tendency is to want to bring one scoped rifle for stand hunting and another open sighted, probably lighter rifle for pushing bush. Add some sort of shotgun best suited for the types of small game that we might see, an extra loaner or backup rifle and maybe a .22 (or a combo gun like the M6 Scout or .22/20ga Savage 24) and that's what I'd prefer to have.
For a waterfowl or small game hunt, I'll usually have either a backup or a pair of waterfowl and upland guns if I'm expecting to hunt a bit of both.
This year I took a #1mk3* SMLE and 7.62 Israeli K98k for two days of deer hunting. I also packed the CZ858 but wasn't able to pick up any soft point ammo so it didn't go out.
Practicing at the range, I come across enough small gunsmithing issues that probably wouldn't be apparent if I'd just taken the guns out hunting once or twice a season, so it's shown me how easy it is to have an unanticipated problem, and allowed me to fix some before the gun made it into the field.
Next year's choice of guns will depend on which guns I get to glass bed, scope and tinker with through the summer. Worst case scenario I'll have a Norinco/Polytech M14 with a scope and a CZ858, with Russian SKS as backup. If I get my Husqvarnas glass bedded, scoped and sighted in, I might take two 9.3x57 rifles, plus another flatter shooting rifle (6.5x55?). I really like collecting milsurps, so I might throw in one or two guns that I've had a chance to sight in and practice with soft point ammo.
For waterfowl, once my Mossberg 835 comes back from the gunsmith, my Win 120 will once again be relegated to backup status. I use a 20 ga Ugartechia SxS for upland game, but usually will have a Savage 24F or other shotgun as back up.