For daytime, I just have the Fantasea light. With the OMDEM5 I rarely need anything, and it is light small, and inexpensive.
For night, I have the iTorch Pro4. As a matter of fact I have three of them, one for me, and two for my wife and her Stylus that shoots pretty darn good 1800i video. Besides that fact that iTorch is the best bang for the buck, it has some great features. It comes with two batteries, and is easy to change if needed. It has a very wide and bright pattern. It has three white and three red modes. For night dives i can use it as a light on low white, and quickly switch to low red to not spook and shoot a subject.
From a video perspective, here is some unedited video with the OMDEM5 and one ITorch Pro4:
[video=youtube_share;RM-bjPKg1ws]http://youtu.be/RM-bjPKg1ws[/video]