Personally, I like playing as Shaka.
Agriculture is often needed for your first Resource improvement; otherwise, you'll likely want Animal Husbandry for your first Resource improvement.
Starting with Agriculture + Hunting gives you a bonus to research on Animal Husbandry.
Early knowledge of Horses is helpful.
Detour to Mining + Bronze Working, then toss in The Wheel, and you've got all of the techs that you'll need for quite a while.
Ikhandas come cheaply with the Aggressive Trait and can be built right away... just as with Huayna, having an early-game and powerful Unique Building can set your Civ apart from the others. Reducing Maintenance on Deity while giving your 2-movement-point early Impis or Chariots an extra Promo, all for half price, gives you a solid edge up that screams spamming an Ikhanda in every City... not something that is so useful to do with a lot of other Unique Buildings.
Aggressive means that your early Unique Unit starts with the Combat I Promo. Toss in free Mobility and not only can you make extremely sneaky strikes on enemy Cities, but you can also pull off Worker steals that leave the AIs saying "What the... LOL!?!"
Yes, you have to be creative about your Worker steals, as no, the AIs are not completely ignorant of your Impis' Mobility Promotions. However, you can set up a lot of 2-turn Worker stealing operations at a time when a lot of Forests haven't been chopped, so the Workers can get "stuck" on their way to safety on the second turn of approaching them, leaving them easy pickings for your Impis to pick off.
Impis coming with Combat I + 3 XP mean that you can start them off with the Cover (Anti-Archery) Promotion. First Strike away with your puny arrows... they bounce off of the hides of my troops, barely causing any damage, while we run in and tear off your Archers' heads.
Starting with a Scout lets you quickly find your first victim and map out their lands for your eventual Worker-farming. Sure, an early Warrior lets you steal a Worker, but then good luck avoiding all of the free enemy Archers that are roaming around the map in a Deity game. I'd rather have map knowledge so that when I come in with my Impis, I can keep picking off Workers during the war.
Axemen will pwn Impis, right? Well, by that time, you will have settled a Horse City or will have stolen one, and can add Chariots to your attacking stacks. Pillage the key Roads in enemy territory (with a sacrificial unit, if necessary) and slow-moving Axemen are no longer scary, with Chariots to easily take them out as the Axemen slowly blunder around in their own lands.
As if that wasn't good enough, toss on 1 more tech and you're at Pottery, earning you cheap Granaries, arguably one of the strongest Buildings in the game (another reason why Huayna is so strong, since Granaries are replaced with his Unique Building).
Sure, it's nice to have a lot of cheap Buildings with a Leader like Mehmed II, but it usually takes a long time to getting around to building them all. Not so with cheap Granaries and cheap Barracks that act as mini-Courthouses, which both come early and which you'll want to spam in every one of your Cities.
Getting +2 Health per City from the Expansive Trait means that you can aggressively clear-cut your Forests, giving you an even greater edge early on in the game.
+25% bonus to Worker Production can often mean getting an early leg-up at the start of the game... it's not too uncommon to have a PH For square or to be able to settle on a 2-Hammer square while finding a GH For or P For square available to give you a total of 4 base Hammers (counting the 1 free Hammer that you'll always get from your City Centre square), giving you that extremely-useful free +1 bonus Hammer at the start of the game, which can launch your game off to an extra-early start.
If you can effectively mess with the AIs, they won't stand much of a chance. Yes, Civs that are further away can build up, but you'll also have access to a larger empire via conquest which can be supported with reduced Maintenance Costs from the Ikhandas. Pick and choose the Cities that you want to capture (lookie here, a nice City with a Gems Resource!), as you can quickly cut off Strategic Resource access in an empire and capture only the Cities that you like, leaving the AIs alive to develop the remaining junky locations while they stay busy building more Workers for you to steal.
Personally, I love messing with the AIs and so Shaka is one of my favourite Leaders. If you're a Lonely Heart, he's still okay for REXing, as cheap Ikhandas and cheap Granaries are still your friends, but his true power shines when you have neighbours and the map isn't completely barren of Strategic Resources.