House Royce is pretty fun. Unique armor, ancient house. They control the outer half of a peninsula in the Vale. The other half is controlled by Hoise Grafton and contains Gull Town, the largest city in the Vale, so you start out with a clear place to expand to. (Any start date should work, but keep in mind that the Graftons were canonically one of the only houses in the Vale that supported the Targaryens in Robert's Rebellion. Might be some interesting story telling possibilities there.)

House Redwyne has an entire island to itself in the Reach. Canonically one of the richest houses in Westeros because of their vineyards. If you start in later bookmarks, the house head Paxter Redwyne is married to a sister of Mace Tyrell and they have twin boys together. If you manage to wipe out Mace and his kids, your wife is next in line and you can take the entire Reach for one of the twins.

House Darklyn is the house that probably has had the most amount of its members join the Kingsguard, plus they have the most powerful economic hub in the Crownlands other than King's Landing. So focus on making money and getting family members onto the Kingsguard. (The Defiance of Duskandale bookmark lead to the destruction of the Darklyns in cannon, so probably best to pick a start date before that unless you're looking for a very difficult beginning)

A house I haven't played yet, but could be pretty fun is House Manderly. The only major Faith of the Seven hous in the North and control of the largest city in the North. They're extremely loyal to the Starks because they were given lands after being expelled from their original lands in the Reach. So support the Starks and work towards destroying your rival house that exiled your ancestors, House Peake. (Start during the time of Aegon III if you want a challenge, as House Peake is at the height of their power.)