There aren't many moves that you HAVE to know – but a good Guillotine is probably of them: Jiu jitsu gives you a lot of choice when it comes to move selection. There is a huge variation among the great champions as to what their main moves where. As you get more fundamental the moves become less optional – it's hard to imagine a world champion who had no elbow escape for example. Among the submission holds I always encourage my students to a strong Guillotine attack. There are few submissions that are as readily available in all aspects of play without a gi than the guillotine. Top or bottom, or ground, set position or scramble – it's pretty much always available at some point after just a few minutes of action. There are many variations – I favor high wrist variations above all others, but great champions have used many variations with great success so find whichever one works best for you. Because you can easily switch sides with your opponents head you only need to be strong on one side with the guillotine. In my case I have a good in guillotine on my left and a good high wrist on my – so I can play sides, but with different variations; but at a minimum have a really strong variation on one side and you will be ready to go!