Which Cutter to Use
What cutter that you use will depend on the shape of your cigar. Cigar shapes can be quite different from one another.
Your most common cigars are what are referred to as straight-sided cigars. Straight-sided means that, other than the slight curve at the head (the side you cut), these cigars should have a level line from end to end. The most popular among these are the Churchill, Corona, Double Corona, Lonsdale and Robusto.
When cutting a straight sided cigar, it is important they you only cut the cap of the cigar. The cap is what holds your cigar together. If you cut off too much, or all of the cap, your cigar can unravel while smoking it.
The picture below will show the cap on a straight sided cigar, and where to make your cut.

You can use any type of cutter on a straight sided cigar.
A Figurado is a shaped cigar.
Most recognized of the Figurados are the Belicoso, Perfecto, Pyramid and Torpedo.
Belicoso is in the shape of a pyramid..
Perfectos are tapered on both ends, which gives them a bulge in the middle.
Pyramid has a small head (the end you cut) and a much wider foot (the end you light).
Torpedos have a pointed head with a straight body.
Most smokers use a guillotine cutter to cut any of the Figurado shaped cigars