It seems that octopuses have have a prefered limb (tentacle?):

Octopuses have a preferred arm

Most octopuses have a favourite arm, zoologists have discovered. This is the first time they have been found to show any bias when choosing which of their eight limbs is right for the job.

The creatures use their trusty first-choice appendage when exploring a new nook or cranny, says Ruth Byrne of the University of Vienna in Austria. She presented the discovery on Sunday at the annual meeting of the Animal Behavior Society in Oaxaca, Mexico. [Nature.com] [via David Harris' Science & Literature]

How exactly does one say which arm it is? Something like 3rd limb clockwised?