Rashi (citing the Sifri) and Ramban (citing Rashi): It implies that his border gets wider as it goes eastwards.

Ramban #1 (citing the Ibn Ezra): Having compared Gad to a lion, he blesses with spaciousness (comfort), because whoever sees him runs away from him and there is nobody to disturb him.

Ramban #2 and Seforno: This implies that Gad received the largest portion of land ¹ - in Eiver ha'Yarden - of all the tribes.

Hadar Zekenim ² : Because it was grazing land, an expression of Harchavah applies, like "Yir'eh Miknecha

Rashi: Because, due to the fact that they lived on the border, they needed to be exceptionally strong. ¹

Rashi and Targum Yonasan #1: It teaches us that, due to the incredible strength of the tribe of Gad, one could recognize the corpses that they had killed, inasmuch as they would sever the arm together with the head ¹ in one stroke.

Targum Onkelos and Targum Yonasan #2: 'And they kill rulers and kings'.

Da'as Zekenim, Hadar Zekenim, Rosh: When the victim would raise his arm, lest he be struck on the head, Bnei Gad would cut the arm and the head with it, until the end of the shoulder.

Kol Eliyahu, Divrei Eliyahu: If one interrupts between the hand Tefilin and the head Tefilin, this is an Aveirah that disqualifies from serving in the army. Gad did not transgress ¹ , so Midah k'Neged Midah, they cut off the arm and head at once.