Here is the full list of all 9 Mad Dog II: The Lost Gold trophies - there are 5 bronze, 2 silver and 2 gold.
Hit all 3 practice targets. ( single player )
Get to the treasure with shooting beaver. ( single player )
Get to the treasure with the Professor. ( single player )
Get to the treasure with Buckskin Bonnie. ( single player )
Hit 6 shots in a row without missing or reloading. ( single player )
Hit 12 shots in a row without missing or reloading. ( single player )
Beat Mad Dog in multiplayer.
Defeat Mad Dog. ( single player )
Get the "good" ending. ( single player )