Löwe, as of June 2020
The Löwe is a lovely tank, and very potato friendly. It has an amazing turret, great gun depression, great ammunition, and it doesn't actively get you in trouble.
Yes it has absolutely terrible damage per minute on paper, but the great penetration of its ammunition, and impressive accuracy, more than makes up for it.
The Löwe won't make you a king potato, but the turret will save you from many mistakes, and the hull sometimes bounces a shot as well. If you at some point learn to sidescrape the Löwe does that really well.
The Löwe does not work well alone though, so if you don't know where to go then follow the other heavies, and find somewhere to park where the enemy can't see the lower half of the front of your tank.
Against enemies of the same tier or lower your turret is more or less invulnerable while pointing straight at the enemy, and your penetration is high enough that you often won't even need to target weak spots if you fire premium ammunition.
Against tier 9-10 the turret is much less reliable, but will still save you plenty of times, just try and duck into cover after shooting.
Potato score: 8 / 10 (highly recommend and always available)