D and D 3.5e
I would like to mention here an idea a friend of mine told me and I immediately wanted it to happen.
Let's say "overarching struggle against central evil"
The gods (Evil, good, chaotic, lawful and everything between) have fallen to a mysterious invasion from demons/devils/Other planes. Their mightiest heroes are killed. They have to resort to those who have little to no change to succeed to restore the lives of the mightiest heroes so they can win the war for the gods.
They are level 20 singleclass characters. No big magic and with a paladin theme/limitations.
Classes available:
Paladin 20(Religious Paladin in all its variety of forms, like Paladin of Slaughter)
Ranger 20 (Nature Paladin. Good BAB and limited spellcasting)
Hexblade 20(Arcane Paladin. Good BAB and limited spellcasting)
Crusader 20(Martial Paladin. Good BAB, strong religious bonds)
Sohei 20(Oriental Paladin. Strong Religious bonds, llimited spellcasting)
Soulborn 20(Incarnum Paladin. Good BAB, Strong religious bonds, limited meldshaping)
Divine Mind 20(Psionic Paladin. Strong Religious Bonds, limited manifesting)
Even if it is a 20th level game, the inability of casting 9th level spells/powers should make things a little easier. In fact, a little too easy. We may need some dragon magazines to survive as a character with that class limitations. Except we don't need the ASF that gives manifesting from level 1 to the ranger. The idea is that we all have limited spellcasting.
And the gods give special and expressed permission to paladins to associate with evil people, if some players want to play naughty. After all, with all the enemies before us, we will have little time to attack each other.
If noone likes that idea, I have no problem in a game with Dungeons and politics.