Nikon SB-910 Speedlight (B&H)
The SB-910 is the top Nikon flashgun, and improves on the SB-800 and SB-900 in a number of ways. What makes the SB-910 stand out over other speedlights by Nikon, is that the flash-head rotates 180 degrees to either side; and the ease with which the wireless TTL menu is accessed. In my opinion these and other improvements, make this a solid upgrade over the SB-800.
Nikon SU-800 Speedlight Commander Unit (B&H)
Wireless TTL flash will open up a wider range of possibilities in lighting in comparison to just using on-camera flash. Even though you can use your Nikon SB-800 to control other Speedlights, using the SU-800 is so much simpler. With the SU-800 you don’t have to go into a menu to change settings or enable the unit, like you would have to with an SB-800.
Nikon SD-9 battery pack (B&H)
I would highly recommend using a battery pack of some kind when you use a flashgun. The SD-9 will really help your flash photography by recycling your SB-900 faster, and thereby give you more consistent exposures from frame to frame.
Canon 600EX-RT Speedlite (B&H)
The on-camera flashgun I most often use and would highly recommend over any other, is the Canon 600EX-RT. Even the previous model would make an excellent choice. What sets the top speedlites from Canon apart from any other lesser speedlites, is the ability to rotate 180′ either way. This opens up a lot more opportunities in bouncing your flash off other surfaces. But what really elevates the Canon 600EX-RT speedlite, is that it has a built-in radio transmitter to give you easy radio-controlled TTL and manual flash from your camera, without added paraphernalia.
my review: Canon 600EX-RT Speedlite
Canon ST-E3-RT Speedlite Transmitter (B&H)
Wireless TTL flash will enable you to be more creative in your lighting, by enabling you to position your Speedlites as off-camera lights. This will open up a wider range of possibilities than just using on-camera flash. Even though you can use your Canon Speedlite to control other Speedlites as wireless TTL controlled flashguns, using the ST-E3 is so much simpler. With the ST-E3 you don’t have to go into a menu to change settings or enable it. Best of all, the ST-E3 gives you radio control over your speedlites.
my review: Canon ST-E3-RT
Canon CP-E4 Compact Battery Pack (B&H)
I would highly recommend a battery pack like the CP-E4. They really help your flash photography is in giving you more consistent exposures. This is because the faster recycling of your flashgun would allow you to shoot faster than with the flashgun recycling from the usual batteries.
Sanyo Eneloop batteries
You do need batteries that recharge (as opposed to disposables), and you also need batteries that can give you enough power consistently. The Sanyo Eneloop batteries (B&H) are renowned for their their very slow self-discharge rate, and for their 1000 charge life-cycle.
What I specifically like about the Pearstone charger, is that it charges each battery individually, and also warns you if any particular battery has become a problem. This is a very important point that is easy to overlook.
Quantum Turbo SC battery pack - (SC = Slim & Compact) (B&H)
For more juice than the battery packs with rechargable batteries, I use the Quantum SC battery pack. As the name says, it is slim and compact – yet offers great capacity.
Since I frequently gel my flashguns to bring the flash WB closer to Tungsten / Incandescent, I use these gels that I cut up and tape to the top of my speedlight’s head. One of these sheets (which – at $6.50 - aren’t expensive), will give you a lifetime supply of these filters. If you use flash indoors where Tungsten lighting dominates, then these filters are an invaluable part of flash photography. Highly recommended.
The Full CTS will bring your flash WB down to around 2900K, more or less neutralising the look of the Tungsten light. The 1/2 CTS will bring your flash WB to around 3800K, which will leave your backgrounds still with a touch of the warmth of Tungsten lighting.