Currently I am using Boone and ED-E as my companions.
Which is everybody else using and why?

My current sniper character has ED-E for the sensors, and Veronica to handle anything that gets too close

Raul and ED-E.
Raul for his awesome Perk and skills with the Gauss/Super Sledge combo, and ED-E for fun.
ED-E has glitched for some reason though, so he doesn't have any weapons, ranged nor melee, and just stays in one spot at all times. Annoying.

even tough boone has a good spotter perk he KSes you way too much, and if you decide to make him melee, it's a waste of companion slot.

Veronica and Rex. I met Veronica on the way to the strip and just stuck with her, love the voice acting. And i helped out king he is kinda cool And got rex i can do without it but its good to have extra 240 lbs of inventory

Raul and ED-E. Though I hate ED-E. That little robot has coerced so many reloads due to deaths. It's only good for 210 lbs. worth of loot conveyance - and its' hostile detection, ringtone thing. Raul, however, is better. I like his sarcasm, his voice actor, how he calls me "boss", and how he's damn good with a magnum. More pluses than ED-E. I'm tempted to just empty its' inventory and let it get dropped by some random enemy, only to get Rex or something. Rex is the only other non-human companion, right?

I play a sniper character. I don't really have any good short ranged weapons besides 'This Machine'.
I usually have Veronica set to ranged using the unique Plasma Rifle, whose name I forget, and Max-Charged Microfusion Cells.
It depends on the enemies we're fighting. If there are robots, I let her go punchdrunk. She is using the Paladin Toaster glove with the added EMP effect. I've equiped her in Recon armor because it's Brotherhood'ish, and not Power Armor... cuz she's not a Paladin.

I have Eddie, too. But he's pretty useless. I just set him to passive and use him to carry my AMR and .50cal rounds (since they're so freakin' heavy).
I only use the AMR on Deathclaws. My silenced sniper is more than enough for everything else.

Because they're a snipers dream, is why

I also have a NCR ranger on call, and I do, call her that is..

ED-E and Boone.

I don't even have to bring a gun with me, just a load of stimpaks because ED-E has the courage of a giant and the defense of a cockroach.

Boone and ED-E throughout the entire first game. In the next game I'm going to lose their perks so will have to compensate....I can't imagine yet but I'm sure it'll be a challenge. I've really liked this combination. I'm Energy Weapons and Boone's a sniper...it's great.

Veronica and ED-E. ED-E is a pretty obvious pick, and Veronica is just sassy and a genius with the Super Sledge. Plus she can wear Power Armor.

Cass (in Blastmaster armor :hubbahubba:) and ED-E.

I'm not sure I agree. I gave him Motor runner's chainsaw (just to carry it originally) and he is constantly using that in melee and he kills nearly anything in one or two swipes. He only gets overwhelmed when swarmed by something powerful like cazadores. It's hard getting him to use a gun sometimes.