Githyanki are amazing melee characters just because Jump is insane in this game. The other day I had Lae'zel leap from one house to the other during the goblin ambush at the destroyed town. It would've taken her 3-4 turns to get across on foot. One leap and an Action Surge later she's cutting down the booyag and threatening the other archer.
Then later they get Misty Step. The sheer mobility of the Githyanki is incredible, and you can always cast Jump before a fight as it doesn't require concentration.
Gold Dwarf is another good choice. Not as flashy as Githyanki but they get even more HP to make you even more of an HP sponge, plus resistance to poison is pretty nice in a game where enemies have poisoned arrows in every fight.
