Sharps loaded with White Powder would be a good choice even for Dangerous Game. The most important things to remember are “Patience” followed by “Shot Placement”. The Sharps is a bit slower to load than say a Ruger number one or similar action but with practice, you can be quick. A lot of coastal grizzlies have been taken with “Single Shots” such as Sharps, rolling blocks and trap doors loaded with Black powder, in my mind at least grizzlies qualify as dangerous game.
However I also think it would be prudent to have a marlin 45/70 cowboy loaded with 10 rounds of Garrett 540gr hammer heads handy just in case