I am guessing you mean klutz and unnerve. If that is the case then yes, they can be useful. First, klutz is an ability that prevents use of a held item e.g a lum berry. Normally this is a pain because holding items is vital to many strategies in competitive play. But it can be used to an advantage. For example, when holding a flame orb it normally would burn the Pokemon holding it but with klutz it doesn't affect the Pokemon. Add trick to swap items and you can burn your opponent doing damage while decreasing their attack power. Something similar is the move wonder room which makes all items held by Pokemon in battle lose their affects.
Unnerve stops the opponent Pokemon eating held berry's. Keep in mind that this only affects Pokemon when the Pokemon with this ability is switched in, not afterwards(so if you sent in galvantula with unnerve and the opponent sent a Stoutland for example then Stoutland would not be able to eat held berry's but any Pokemon sent after would be able to). Berry's are often used to heal HP or status conditions as well as decreasing damage from attacks and preventing this can be very useful in battle. Similar moves include pluck and bug bite which eat your opponents held berry,stealing it's affects. I hope I helped. (P.S you can look up ability's so try not to post this type of Q unless you still not clear on them)
