I remember the droid Razr Maxx and the Maxx HD. I used a Razr Maxx HD up until two years ago when I lost it in the ocean when our boat sank. It Was a great device, had a great battery and even a mini HDMI port.
The MSGM8 that I used on Cricket. When Cricket switched to AT&T's network, it was not compatible. I was forced to give up the 1.3 Megapixel camera and switch to the Moto E. The Moto E died and I now use a Moto Z.
Nokia X6 with Symbian S60^5 in 2010 could be called as a Smartphone but if talking about modern Smart OSs then it would be Samsung Galaxy Grand Quattro Duos GT-I8552 with Android 4.1.2 in 2013. I also had Nokia N70 ME with Symbian S60^2 in 2008 which was quite capable phone for its time but I don't think it could be considered a smartphone.