I rolled and played a Barbarian/Warlock.
I had intended to roll up a Hexblade (new at the time), but my rolls were 18 17 17 14 13 5, and my first thought was if I took variant human I could have three 18s in my physical stats!
Of course I could've made a great Hexblade with those rolls (or anything else!) but the idea of a 'perfect human' stayed with me and evolved.
I won't bore you with yet another (awesome, BTW!) backstory, but once I'd decided to make my three physical stats 18, Hexblade seemed pointless. I wanted to put those three 18s into good use, while still being a warlock.
So I started as Bar 1, then switched to warlock (fiendish bladepact) up to Bar 1/ War 5, then got to Bar 3/War 5 (I chose the Zealot subclass for story reasons), then switched back to warlock. I'm Bar 3/War 11 right now.
At first glance the two classes seem incompatible because you cannot cast or concentrate on a spell while Raging. This is a problem, but it ceases to be a problem if you don't have any concentration combat spells and don't intend to cast during your rage.
So pre-cast armour of agathys, then on round one cast a pre-asskicking fireball, Rage and move into melee, trying to provoke as many opportunity attacks as you can. After that it's all melee. Your damage resistance makes your AofA last over twice as long, and by the time it has gone away you constantly gain and use THPs from Dark One's Blessing. The rest is gravy!
Tremendously effective and enjoyable, even though my Cha is only 14. My Int of 5 ceased to be a problem when I got a Headband of Intellect.