The games i plan on playing are GTA V, The Witcher, Batman Arkham Night, Dead Island 2, Killing Floor 2, Toxikk, and if they come out with a Black Ops III I will be playing that as well
oh yeah and id prefer the keyboard to be mechanical
If you are not playing games online competitively, it will all come down to personal preference, meaning it will be subjective, meaning our advises are quite pointless .
I suggest you go to a store or similar and just test them.
Blackwidow Ultimate is a great choice but keep in mind that it is quite expensive.
If you are low on budget and looking for good quality keyboard, you might also consider the Deathstalker Essential.