A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head.
Rubber mallets
A wooden mallet
Stonemason's mallets of plastic, wood and steel
An iron mallet with copper faces. Solid head copper mallets are produced with a round or square head
A sledgehammer is a tool with a large, flat, often metal head, attached to a long handle. The long handle combined with a heavy head allows the sledgehammer to gather momentum during a swing and apply a large force compared to hammers designed to drive nails. Along with the mallet, it shares the ability to distribute force over a wide area. This is in contrast to other types of hammers, which concentrate force in a relatively small area.
20-pound (9.1 kg) and 10-pound (4.5 kg) sledgehammers
A straight peen sledge hammer from an 1899 American book on blacksmithing
Spike maul used for driving railroad spikes during track construction