Abnormal

The Deviant Type (奇行種) (also known as Aberrant or Abnormal Titan) is an uncommon type of Titan which possesses unusual intelligence and performs unpredictable actions.

Description
Unlike the typical Titan which attacks and devours humans on sight, Deviant Type Titans may choose to ignore humans and exhibit unpredictable behaviour; often resulting in them causing larger damage as they disrupt important strategical locations.

Invasion of Trost
During the invasion of Trost, a horde of Titans entered through the breached gate and the soldiers and human forces had to take action.

As Eren Yeager's group was heading towards the middle of the Trost district, a deviant Titan jumped out of nowhere and grabbed Tomas Wagner in its mouth. The rest of the group looked on, horrified, as the Titan swallowed him whole.

Another Deviant Type appeared and charged straight towards the rear exit of Trost,where a group of citizens were gathered and trying to escape. It ran so fast that the elite guards stationed in that area couldn't keep up with it. Mikasa Ackerman appeared and sliced the nape of its neck to kill it, dulling her blades in the process.

Female Titan Arc
The Survey Corps went on its expedition outside Wall Rose and on the way a Deviant Type suddenly appeared towards the right flank. It completely ignored the soldiers at the outer guard and charged straight towards the centre of the formation. Armin Arlert  watched as Cis and Ness were forced to fight it, cutting the tendons of its foot making it fall and subsequently killing it.

After the Clash of Titans Arc
After Eren and Ymir were kidnapped by Reiner and Bertholdt, they stopped by in a Forest of Giant Trees between Wall Rose and Wall Maria. As they were resting atop the branches, a Deviant Type Titan was casually lying beneath them and it seemed to watch their every movement. Another deviant was seen as it hesitantly watched Eren and Ymir from distance, instead of attacking them right away.