I used to play a lot of World of Tanks. Not going into details, but I figure I made the game free for a lot of people.
My favorite tank lines, in general, were the Americans. Turreted Tank Destroyers like the Wolverine, Slugger, M8A1, Hellcat, etc. etc.? Fast but durable Heavy Tanks like the T1HT and M6? Well-rounded Medium Tanks like the M4 Sherman, Ram II, M26 Pershing, etc. etc.? Awesome low-tier tanks like the M3 Stuart, T18, T82(now both moved to the fucking Artillery line, god dammit), T1 Cunningham, M22 Locust, etc. etc.? And all that wicked gun depression for hill fighting? HELL YEAH!
Of course, there were several other tanks from other lines that I enjoyed as well, most notably the Soviet T-34-85 and KV-13 Medium Tanks and BT series and T-46 Light Tanks, the French FCM 50t Premium Heavy Tank, the German Panzer III Medium Tank, the British Cruiser Mk.III line of Light and Medium Tanks(practically my second favorite line behind the Americans) and the Japanese Medium Tanks(the Type 2597 Chi-Ha at Tier 3 is a fucking beast with its 47mm death cannon).