Unsettled eyeshapes

Three in a row.  

See straight three. Black can almost fill the eyespace with two stones, leaving White with a dead eyeshape.

Bent three  

See bent three. Same comment as above.

Pyramid four  

The shape here is known as the Pyramid Four. Black has a nakade at 1, the vital point. White is reduced to a single eye, which Black can almost fill with straight three or bent three. White is dead.

Cross.  

In this cross of size 5, Black can kill White by playing at 1. Next he can almost fill with a pyramid four.

Bulky five.  

This shape, nicknamed the 'bulky five' in English, is killed by the placement at 1. Next, he can almost fill with a squared four. White does have a ko threat to live at a.

Rabbitty six.  

This is the so-called rabbitty six. After 1, Black can almost fill this eyespace with a bulky five and White can do nothing about it. As with the bulky five, White can threaten to live at a as a ko threat.