I like farm Trav, Ball, cow's, the most
I also like to find the keys for the Uber you'll need three different key (key of terror, key of hate and key of destruction) to make one portal and you want to open three portal and you also want to open three portal at the same time (it's mean you need three set of key total of 9 keys) for make sure to have all the items (Brain, Eye and Horn) of each portal to open a last one (4 portal total) for the uber and now prepare yourself to kill Mephisto, Diablo and Ball at the same time!
Key Of Terror Location: Act1, Black Marsh, The Forgotten Tower, have to kill The Countess Cellar Tower lvl 5
Tips: When you enter to the door from each lvl look at your character you always want to go to the left where your character facing and you'll find the door!
Key Of Hate Location: Act2, Arcane Sanctuary, kill The Summoner
Key Of Destruction Location: Act5, Halls Of Pain, Halls Of Vaught, kill Nihlatak
Tips: When you start in Halls Of Pain if you are on the left side of the map the door will be on the RIGHT TOP of your map, but if you are on the right side of your map, the door will be on THE BOTTOM of your map to find the Hall Of Vaught door!