I own a ton of different accessories that I use whenever required, some cheap, some expensive, some store bought and some self made. This list contains my most frequently used store bought accessories as well as a few things to keep in mind if you are considering using them for your own film projects.
I wouldn't take this tripod with me on travel, but for all of my shoots and filming tutorials it is ideal. I don't have to worry about accidentally breaking it and it can hold up to 7kg which is much more than I need to support my Canon 5D Mark III and the EF 24-70mm F/2.8 lens.
The only issues I sometimes have with the H2N is that it picks up handling sounds and ambient noise a little bit too easily. You also definitely want to get a wind shield for the recorder if you intend to take it outside.
I did have to tweak the settings on the app a little bit to disable an overly aggressive noise gate, but I am much happier with the sound from the Rode SmartLav than I was with the sound from the H2N - for tutorials. The H2N does not have bad audio by any means and I still use it for all of my short films, but for talking to the camera I prefer the dry, direct sound from the lavalier microphone.
Listing SD cards as accessories might sound silly, but I actually have a little pool of SD cards and only one or two of them that I actually use. The most important aspect when shooting video at high definition is to use an SD card that has sufficient write speed.When filming with my Canon 5D Mark III at 1080p I need my SanDisk Extreme 64GB SDXC Memory Card with a write speed of 60MB/sec to be able to capture the video stream without the recording being aborted due to buffer overflow. You want to get at least a Class 10 SD card when filming with a DSLR. If you are shooting with a compact camera or at lower resolution a slower SD card will likely suffice.
I do find that it is a little bit small at times and you will have to be careful that your subject doesn't leave the area of the popup screen, but it makes life a lot easier than having to lug around and set up a full blown green screen backdrop every time.
Unless you plan to mount a huge camera on the slider and have a professional set of camera tripod legs to hold it all up, I would recommend going for the carbon fiber model instead of the Pro. You will likely get much more use out of a model that is a fraction of the weight and therefore easier to take with you and set up.
Quite frankly I don't usually have it mounted on top of my camera as I'm not a big fan of the 'light directly from the front' look in my videos, but I use the LED light a lot off camera or bounce it off walls to fill in dark areas or even out the light when shooting in bright environments.
This is a fairly affordable field monitor and while the quality isn't bad, it didn't quite win me over mainly due to it being a bit clunky to set up. I am still in the market for a smaller, more portable field monitor and am looking for a potential wireless solution.