I am indeed a left-handed mouse user. I've tested at least 100 mice in my quest to find a great left-handed mouse. For me, there are several that are tolerable, but none that are perfect. I'll name a few off the top of my head that I've tried and I'll list the flaws I can recall.
Currently, I am using a Zowie ZA11. It's very near perfect for me. I have two gripes with it. First, the shape of the mouse is just ever so slightly too high in the palm for me. I have pretty large hands and I feel that the ZA12 will be too small for me. The overall size of the ZA11 is very good for my hands, but the palm is just a bit too high for perfect comfort. Also, the weight of the switches in both mouse buttons feels like you have to use all your might to actuate them. In reality, they're probably not all that much worse than other mice, but they are very notably more stiff, and that's a big turnoff for me.
Razer DeathAdder LH - This was great for a long time. It's still pretty good, but the mousewheel is utter garbage. It's really the only ergonomic mouse for LH that is even remotely decent.
Razer Naga LH - Just awful. Feels like something you'd get in a happy meal box.
Logitech G400/G400s - Not terrible feeling at all, but you'll only be able to use the two buttons and the wheel effectively. The G400 had a tendency for the shell of the buttons to pop up over the top of the mouse shell itself, which would then grind together as you tried to click. The G400s seemed to resolve that.
Other Logitech G series mice - These are all either only 3 button mice, or they're built with side buttons only on the left side of the mouse so they would be extremely difficult to utilize in your left hand.
Steelseries Sensei / Sensei Raw - This family was so damn close to perfect. It felt just exactly perfect. The two flaws from the Zowie ZA11 were non-factors with the Sensei. The palm height was perfect, and all buttons as well as the wheel felt very crisp and responsive without being too stiff. The only issue with the Sensei was unfortunately a huge issue: the laser sensor itself. It's notoriously known for having significant negative acceleration. It did seem consistent and I don't think using it puts you at a huge disadvantage compared to better sensors, it just feels awkward to experience the bad sensor, especially when you use it for a significant length of time and then try something better. You'll instantly hate the feel of the Sensei's cursor response
Roccat Kova - Mouse felt very cheap. The coating seemed to react poorly with any hand sweat or oils, even if they were minimal. The wheel was very good. The button response was fine, but the coating was just finicky.
Razer Taipan - The whole mouse body had an awkward feel to me. It might have been better with smaller hands, but it just felt strange. The side buttons were super thin so they required a very specific and angled push with the thumb to actuate. Sensor was fine if you kept the DPI reasonable, and the regular buttons felt OK. Synapse sucks.
Razer Ouroboros - Man, what a great idea this was. Unfortunately it's super uncomfortable to hold, and it's wireless, so it suffers from the feeling of latency that all wireless mice have. It's possible I didn't give it long enough to grow on me, but it felt awful from the beginning right up to the day I put it back in the box. Even the very awkward R.A.T. mice felt much better than this.
There are also a lot of mice that appear to be ambidextrous but they're generally missing buttons on the right side of the shell which makes them RH only. Some notable ones are:
Logitech PRO G
Dream Machines DM1 Pro - This one made me very sad. It's basically a Sensei clone with a much better sensor, but they had to omit the right side buttons so it's worthless. :-(
That's all I'm going to list for now, but I'll check back later. If you have any questions regarding specific mice, fire away and I'll let you know if I've used it and how my experience went.