ORIGINAL: bigbulls
The 30-06 will easily kill anything from rabbits to moose and everything in between, the biggest of black bears included. Although it seems that it not suitable any more for hunting anything larger than deer, depending on who you talk to. Seems you now need the latest ultra mag to do that.
If I were after big Grizzlies I would opt for a bigger cartridge, just in case I suddenly became the main menu item, but the 30-06 will take them down as well.
The 30-06 is an excelent choice for a "do all" cartridge.
Second the above. The only game I might want more gun are grizzlies. Though lots of folks use the 30-06 on them as well.