A hotshoe flash (IMO) is one of the most important accessories for a DSLR. However, many new OEM flash units are quite expensive. B&H lists new Canon hotshoe flash units at prices from $200 USD (320EX II) to $470 USD (600EX RC) and there are photographers who cannot/will not pay those prices...
Third party flash units are often less expensive but, you need to be quite careful that these units meet your needs. I want my flash units to have TTL exposure control, high speed sync and slave capability. Manual operation is "nice" but, I can live without that...
My very first Canon hotshoe flash was the 420EX which I purchased along with my 10D camera as my first entry into DSLR photography about fifteen years ago. I still use this flash! It doesn't have manual control but, does have the other bells and whistles that I want and the exposure with any of my DSLR cameras is right on - including bounce flash exposure!
Another plus for the 420EX is that this is the smallest Canon OEM full size hotshoe flash that I know of. The 220EX and 270EX models are much smaller but, these cannot really be considered full featured flashes.
I use my 420EX flash along with the Joe Demb Flash Diffuser Pro and have always been happy with the results. In addition to the 420EX, I also have a 320EX, 500EX and a 600EX RC, as well as the tiny 270EX-ii. However, when I am packing for minimal equipment, I will often select the 420EX as my go-to flash because of the relative small size and light weight. It is also mice for fill flash since it doesn't weigh down the camera/lens terribly...
Although the 420EX doesn't have manual control, it does have TTL exposure control which is quite accurate with Canon DSLR cameras, it is also capable of HSS as well as slave capacity.
Recently, I was shopping for a flash to equip the Canon 350D DSLR camera that I am donating to our dog rescue group and was quite surprised to learn that 420EX flashes often sell, used, for $50 USD or less (including USA shipping) on eBay. That is quite a bargain and, at that price, there really is no reason for any Canon user not to have a hotshoe flash.
There are copies of the Joe Demb Flash Diffusers selling on eBay for less than $10 USD.
http://www.ebay.com/itm/Flash-Reflec...cAAMXQlgtRtAPf
That unit combined with the 420EX can produce some very nice lighting from bounced flash...