Assuming I'm one of those magical FPS pixies with extradimensional storage space, but still want to use real weapons (because, frankly, made up fps weapons can do whatever you want...)
Primary 1: Mechem NTW-20 - Because nothing any other real gun can do says 'I am a one man apocalypse' like killing a base commander by shooting through hardened concrete walls, turning three parked helicopter gunships into burning wreckage and setting fire to a fuel dump in under four minutes, from a mile away, on your own...
Primary 2: Vektor CR-21 - Because they're even more reliable than an AK74, look like they ought to fire shurikens and lightning and have the not inconsiderable advantage of a bullpup layout. They're basically a sealed box made of ballistic plastic with a lot of space inside it and a few solid hunks of metal. You can drop them in mud, drag them through a desert and hit somebody with the buttstock and they pretty much won't even lose accuracy, let alone jam or break.
Secondary: Calico M-950 machine pistol with a carbine clip - The ability to run around carrying a machine pistol with 100 rounds to a clip is, well, awesome, in the truest sense of the word. If I'm feeling posh, it's recognised as being in the same accuracy category as a standard semiautomatic military sidearm, so I might even stick a red-dot site on it.
But really, who would ever need to know where the bullets are going to go? We're talking about a machine pistol that you can keep firing for eight seconds before you run out of ammo, for gods' sakes! Sit and count eight seconds, out loud. Imagine that between each number you spoke, twelve bullets hurtled out of a screaming machine of death in your hands and in the general direction of people you didn't like...
Hand to Hand: My winning personality and rapier wit - Also, a trench spike. The only reason I want to be using a hand to hand weapon is because I am forced to by the environment or the sheer number of assailants. In either case, I want something that is lethal when swung wildly like a maniac and that will not get stuck in people.
Explosive Implement: Multiple detonator mediated explosively formed penetrators - Okay, so I need something that just plain goes 'kaboom'. But I might also need something that can kill a tank. And I might also need something that can turn an APC full of enemies into shark chum (and that isn't a 36 kilo boomstick with an effective minimum range of several hundred metres). A toy like this is all these things. It's a box with an array of detonators arranged at the back, lots of explosives in front of them and a tantalum-molybdenum alloy dish stuck on the front. Depending on the order and pattern of detonators employed it can be a claymore mine, a normal EFP or a poor-man's shaped charge penetrator for killing tanks. What's not to like?
Grenade: Hornet's Nest OC/CS grenades - they're a sort of riot grenade. They scatter dense rubber balls over the blast area, pummeling people to the ground. They also spray a mixture of high purity chilli extract and CS aerosol gas. Do you think you'd still feel like fighting after one of those rolled into your holdout? I don't want a grenade for throwing across a battlefield, I want a grenade for clearing rooms...
Other: Hmmm, staying in the real world, I suppose I'd have to go with the quintessentially modern lethal weapon, a big, sturdy car. Personal security operatives are usually more highly trained with a car than they are with guns and hand to hand combat combined, and that's because they're more useful, more dangerous and safer to use than the other two.