Mono-Normal is likely the toughest team one will ever try to assemble. Here's what I have so far (note adherence to the Item Clause):
-Staraptor @ Choice Scarf, Adamant, Intimidate
EVs: 252 ATK, 252 Spe, 4 HP
Brave Bird, Close Combat, Quick Attack, U-turn
Choice Scarf Staraptor is amazing on paper for a lead. STAB Brave Bird and Close Combat are staples for an offensive build, U-turn lets it scram if the initial matchup is unfavorable (not to mention break Focus Sash), and STAB Quick Attack is probably something most teams won't expect to allow it to play the role of a revenge killer if it U-Turned earlier.
-Girafarig @ Choice Band, Jolly, Inner Focus
EVs: 252 Atk, 252 Spd, 4 HP
Zen Headbutt, Crunch, Body Slam, Earthquake
Textbook Physical Choice, basically. STAB Zen Headbutt is what the doctor ordered to go up against Gengar and Machamp that would otherwise try to run the table. Earthquake is your answer for things like T-Tar and Jirachi (note that Inner Focus stops the latter's Iron Head/Serene Grace combo cold, as well as every Fake Out user), STAB Body Slam is for use against speedy bastards when you're not worried about Guts, and Crunch is a generic catch-all (Rotom especially, who tends to give Staraptor fits) with a chance to lower defense one stage.
-Bibarel @ Expert Belt, Careful, Unaware
EVs: 252 HP, 252 Def, 4 Atk
Waterfall, Super Fang, Superpower, Rock Climb
The classic Bulky Beaver EV distribution, but there the similarity ends. Super Fang dents anything that isn't a Ghost-type, after which Superpower can usually win it, as the majority of monsters you'll want to use this combo on are Rock, Steel, or Blissey. Unaware helps Bibarel bash through screens, STAB Waterfall is a kill move of choice (if it comes in on Castform's rain, it gets even better!), and STAB Rock Climb not only packs more accuracy than Stone Edge or Fire Blast, it has a confusion chance as well. A special sweeper like Gengar that packs TBolt can probably OHKO this thing, however.
-Porygon-Z @ Life Orb, Modest, Adaptability
EVs: 128 HP, 252 SpA, 128 Spe
Tri Attack, Dark Pulse, HP Fighting, Agility
Playing this set is quite easy: After one Agility, the only way to get a solid hit in edgewise is with Scizor's Bullet Punch (or the odd STAB Mach Puncher). Tri Attack is your bread and butter, with the other two moves are saved for anticipated switches to Ghost-types and Rock or Steel-types, respectively. This thing should never be in the fray for more than 3 turns, however, and should only be switched into an attack if Wish is impending (see the next entry).
-Blissey @ Leftovers, Timid, Natural Cure
EVs: 252 HP, 252 SpD, 4 Spe
Wish, Seismic Toss, Protect, Toxic
Seriously, who didn't see this coming? Protect scouts a counter and buys a turn for Wish (which Porygon-Z will appreciate tremendously), Toxic lets it spread status around, and Seismic Toss is for when you NEED to attack to finish off a would-be sweeper.
-Castform @ Damp Rock, Modest, Forecast
EVs: 80 Def, 252 SpA, 176 Spe
Rain Dance, Weather Ball, Thunder, Ice Beam
I'll admit, this guy's something of a gimmick, but there is no better counter for weather teams at the moment. Ideally, you want to switch it into rainy conditions so it can start nailing the foe right away, but just in case, it packs its own Rain Dance. With the wet stuff coming down, STAB Weather Ball has a staggering BP of 300, which will usually either OHKO or force a switch unless the foe has Water Absorb. Ice Beam is a check for Dragon and Grass types as well as something to hit Quagsire with, and Thunder's perfect accuracy in rain combined with the same paralysis chance as Body Slam makes it incredible for hammering any non-Ground or the odd Electric such as Electivire, Jolteon or Lanturn (the last one with Volt Absorb) on the switch, as well as frying all but Quagsire that try the Water Absorb trick. A Rain Dish/Leftovers Ludicolo is something to look out for, however.