Electromagnetic ball (or EMP ball): easier to catch electric and steel types x2. Also works on Pokemon like Porygon.
As for items: MindReader (or some better name, hopefully)-same effect as the ability Telepathy, only as a held item. However, it only works 85% of the time. If it fails, this message is displayed: [Pokemon]'s MindReader malfunctioned! If it is successful, it displays the same text as Telepathy.
???(can't think of a name)-allows gender ratio of a Pokemon to be modified. Works like this- it's a key item that can only be used once a day. You select a gender, then it lets all the wild Pokemon be one gender (if it can have genders) for the next 3 minutes. In breeding, what ever parent holds it, the offspring will be the parent's gender (i.e. if the mother holds it, the offspring will be female, even if it something that has a weird gender ratio, like the starters or fossils) also works once a day as well.