The answer to the above picture should be, "Every 40K player." No matter what you collect or play, you should be able to find a use for a rhino, so if you find one cheap, snap it up!
Anyone playing marines, chaos marines, or most of the variants should be able to find a use for it directly, same with Sisters of Battle. Easy enough.
But even if you don't play an army that has "Rhino" listed as a transport option, you can get use out of one. And given how frequently poor abused rhinos and rhino-chassis vehicles find their way onto ebay, they are pretty easy to come by.
If you play Orks, loot that sucka! It makes a great base for a looted wagon, trukk, or battlewagon. Bonus points if you have a regular marine opponent you can make it look like you captured it from.
Imperial Guard players could use it for conversions as well. Use it as the basis for a command chimera, or perhaps a hydra or other variant tank.
And everyone can use it for terrain! Wreck it up and turn it into a terrain feature. Take bits off and use them on the bases of your larger models.
Everybody's bits box should include a rhino! So next time you see a neglected rhino, pick it up! You'll be glad you did.