I've had great success soloing my Bot/Traps. Almost as strong defenses as /FF, with better debuffing. Rarely die, and then only vs EBs, but most of them go down without too much trouble. But really, any MM powerset combo can solo very well, I doubt any combo find EBs too much to handle (/poison and /traps combined with ranged henchmen probably has it easiest though)
Icelock - Ice/Storm Controller
Command Bot 1 - Bot/Traps MM
It really depends on what's fun to you. Do you want to buff, debuff, a bit of both?
Personally I would say traps is the most fun, I also like poison, TA and dark. I dont think I could play forcefield though, not really enough action for my tastes.
My MA IDs:
Fiend Space: 211464
/traps has the best 'alpha'taker-powers. Seekerdrones, acid turret, poison trap, call trops (not on EB/AV) or even grant inv->detonator. Wide range of debuffs and buffs (FFG ftw). Poison imho is 2nd down best solo, awsome ST debuffs but will start lacking once you face too many mobs. And offcourse, allrounder dark is still a favorite set, good heals, great debuffs and most is good AoE.
Pramairy they all do pretty well, bots for great extra +def or zombie for some lovely melee damage (poisontrap ftw again!). Ninja seem to do pretty good as well, although tier1 pets get a KB power wich can be somewhat annoying.
50)Sinergy X/(50)Mika.
(50)MaceX/(50)Encore
Sign the petition, dont let CoH go down! SIGN!
Traps is great fun, as people have said. Lots of placeables, a dead handy little floating Force Field generator (which isn't a toggle).
Primary is up to you really. I'm really enjoying my Thugs / Traps. Lots of ranged cone damage, cool personal weapons (if you take them. Empty Clips is too cool not to take, at least for a bit) and a fun level 18 power in Gang War (excellent summoning them on a Council Archon and watching him roundhouse-kick 10 of them to death in one move while you cunningly place a poison gas trap at his feet. Watch that fascist puke)
Robots/ Traps for great RP synergy as well packing a fair bit of fire power. Also you cant help but think that the robot pets have character.
@Boy Wonder
Quantum Flash - Ill/Kin Controller
Leader of the Legion of Heroes
With just about any MM you'll be set for soloing for levelling, and EBs shouldn't be a problem really at all.
It's how far you want to take it and push the build and push what you can do. If you want to up the stakes and go for soloing things like AVs then some of the builds mentioned above are the way to go.
I have a bots/traps MM and love it. I was rolled for concept (I wanted an evil scientist with evil robot minions and traps fitted the gizmo's & inventions ideas the best - also I wanted a retro almost steampunk raygun... hellooooooo i11 
).
I love robots, because, well, I love the robots. Really nice, characteristic and unique models. Lots of lovely death ray laser goodness.
Traps is just great fun. It's really interactive and you have a couple of choices of ways to play. You can be evil and spiteful and methodical setting up devasting traps and kill areas and luring enemies to their doooooooom...
Or you can be an absolute siege machine and just march up to stuff and drop your evil wares at their feet .
I guess easy depends on how you define easy. With /traps you'll be a very involved MM, interacting a lot, and managing your henchmen and gizmos. Some other sets are a bit more stand offish and require less interaction.
I've had huge amounts of fun with it, and doing things like standing toe to toe solo with a really [censored] off Hero level Valkryie and she never hits you is just fantastic fun and a great payoff for pushing what you have available as much as you can .
Traps is an excellent secondary and, with the exception of forcefield, the only one to provide you with mezz protection (as well as your minions of course). Some great utility and prospects for tactical play too.
For primaries, I do love my bots, but I'm also finding thugs really fun to play - it has better attacks than most other primaries, with the cone in particular being better than most, if not all, the rest (although the endurance cost for it is obscene) allowing you to get more involved in the action.
But like others have said, none are terribly difficult to solo - it's one of the easiest solo-play ATs in the game, so pick whatever takes your fancy
@Hakeswell
Union Ilservian, Evinlea
Defiant Expeditor, Hakeswell
Arc: 70119 Hellion Initiation
... easiest to solo?
I have never played MM before and was wondering which powersets contained most fun and also which is easiest to lvl solo as I have always had problems teaming on CoV?
Thanks
Golden-Phoenix - Lvl 50 Fire/Fire Tank
Oodja Nikabolokov - Lvl 50 SS/WP Brute
Baby-Phoenix - Lvl 50 Peacebringer
How much wood would a woodchuck chuck if a woodchuck could Chuck Norris?