Knights in 2Moons are great for parties and soloing due to their high defense and good AOE skills. If you have a two hand mace knight it will be easier to AOE in PVE due to the skills that you get in the Two Hand Class (2moons gold) as well. Berserk and Genocide are great skills to use in PVE in combination with Mace Bash and Solar Evil.
If you are a Mace/Shield knight that will cause you to have limited AOE skills, you will have very high defense due to the shield and the high damage skills of mace/shield such as Blind Jab and Bounce Defenser. Player Vs. Player (PVP/Duel) Note: This is for high level (2moon dil) PVP when you have access to all of your skills. Knights can be very dangerous in pvps, you just have to know who you are up against and their weaknesses as well as yours.