Civ 5

[Jackalope]

Wtf? You can take cities with ships? I didn't even know that :S

Yep, and it's much easier. I always take the coastal raider promotion on naval melee units for that very purpose. I don't use melee ships for naval combat much so the boarding party promotion isn't nearly as useful for my play style.

I'll take a city down low enough on health with ranged units so that I can take the city with one attack - if you don't, you're going to almost certainly lose the unit to the city's ranged attack on the next turn. So the tactic is to shell with ranged units til the health bar is at or near zero and the attack preview shows that the you'll do enough damage to take the city without taking enough damage to destroy your melee unit. By the time your ranged units have taken the next target down, you'll have healed enough to use the same unit in that role again.

You don't usually need more than one melee unit per naval combat group to pull this off. You may occasionally need two if the tactical situation is such that your melee unit can be targeted before it can make it's attack. I tend to keep them back behind my ranged units just close enough to reach the city and attack in one turn - so unless an unseen unit pops out of the fog of war it's safe.