There are three basic cycles of cross-sections: flat, half-round and round. There are individual styles of cross-sections for special work, eg. Mechanics` Pliers.

flat,
eg. for secure working with Combination Pliers

half-round,
eg. Long Nose Pliers without side cutter. Their flat, round jaws are also suitable for soldering work

round,
e.g. Electronics Pliers to bend wire eyes