Gunnar or Gunner is a valkyrie

Valkyrie

In Norse mythology, a valkyrie is one of a host of female figures who decides who dies in battle. Selecting among half of those who die in battle , the valkyries bring their chosen to the afterlife hall of the slain, Valhalla, ruled over by the god Odin...

 in Norse mythology

Norse mythology

Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...

. Her name means "battle" and is cognate with the English word "gun

Gun

A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...

". She rode a wolf and took part in selecting the dead warriors together with two other Valkyries in order to bring them to Valhalla.

Rök Stone

The earliest attestation of the name is on the Rök Stone where it occurs as part of a kenning

Kenning

A kenning is a type of literary trope, specifically circumlocution, in the form of a compound that employs figurative language in place of a more concrete single-word noun. Kennings are strongly associated with Old Norse and later Icelandic and Anglo-Saxon poetry...

 for wolf:

Þat sagum tvalfta, hvar hæstR se GunnaR etu vettvangi a, kunungaR tvaiR tigiR svað a liggia.

Translation:

I say this the twelfth, where the horse of Gunnr sees fodder on the battlefield, where twenty kings lie...

Völuspá

Gunnr is also mentioned in Völuspá

Völuspá

Völuspá is the first and best known poem of the Poetic Edda. It tells the story of the creation of the world and its coming end related by a völva addressing Odin...

:

Sá hon valkyrjur

vítt um komnar

görvar at ríða

til Goðþjóðar:

Skuld hélt skildi,

en Skögul önnur,

Gunnr, Hildr, Göndul

ok Geirskögul;

nú eru talðar

nönnur Herjans,

görvar at ríða

grund valkyrjur.

Darraðarljóð

And in Darraðarljóð

Darraðarljóð

Darraðarljóð is a skaldic poem in Old Norse found in chapter 156 of Njáls saga. The song consists of 11 stanzas, and within it twelve valkyries weave and choose who is to be slain at the Battle of Clontarf . Of the twelve valkyries weaving, six of their names are given: Hildr, Hjörþrimul,...

:

Vindum, vindum vef darraðar ok siklingi síðan fylgjum! Þar sjá bragna blóðgar randir Guðr ok Göndul, er grami hlífðu.

Prose Edda

In the Prose Edda

Prose Edda

The Prose Edda, also known as the Younger Edda, Snorri's Edda or simply Edda, is an Icelandic collection of four sections interspersed with excerpts from earlier skaldic and Eddic poetry containing tales from Nordic mythology...

 Gunnr is singled out along with Róta

Róta

In Norse mythology, Róta is a valkyrie. Róta is attested in chapter 36 of the Prose Edda book Gylfaginning, where she is mentioned alongside the valkyries Gunnr and Skuld, and the three are described as "always [riding] to choose who shall be slain and to govern the killings." Otherwise, Róta...

 and Skuld as one of the valkyries who always ride out to choose the slain and decide battles:

Guðr ok Róta ok norn in yngsta, er Skuld heitir, ríða jafnan at kjósa val ok ráða vígum.