Spur gears are inexpensive to manufacture. They cause no axial thrust between gears. Note that two mating helical gears must have equal helix angle but opposite hand. These are found in automotive transmissions, and any application requiring high speed rotation and good performance. They are more expensive to manufacture.
Helical gears create axial thrust.
Crown gears, one gear is flat, has a pitch angle of 90 degree. Similar to spiral bevel gears, but connect non-parallel shafts that do not intersect. Hypoid gears are stronger, operate more quietly, and can be used for higher reduction ratios than spiral bevel gears. They also have sliding action along the teeth, potentially reducing efficiency. Hypoid gears are found in auto differentials.