30-06 and 375 H&H for versatility...the 270 for the most common application of thin skinned deer-like animals in NA. Its cheap, shoots flatter than just about anything out to 400 yds, not a lot of recoil, good enough bullet selection for bigger stuff like moose and bear. For pistol cartridges, Scott made a good point about the 38 special. Enough power for 90% of applications, light recoil, really cheap to shoot, variety of bullets.
