Mardu Control? (Modern)

A heavier (and cheaper - no Lilianas, no Thoughtseize, semibudget mana base-) version of a Mardu Control/Midrange deck (other versions run 4x Lingering Souls, 4x Young Pyromancer and 4x Bedlam Reveler instead of planeswalkers and Olivia Voldaren and not so many lands). You should try to stabilize till midgame with removal and disruption and when the opponent runs out of gas start playing your Olivia Voldaren or your planeswalwers.

Your game should be like this:

• Turn 1 Inquisition of Kozilek, Fatal Push or Lightning Bolt early creatures or mana ramp.
• Turn 2 Same + now you have Lightning Helix and Terminate available. Night's Whisper is a good option if your oponent isn't doing anything relevant.
• Turn 3 Lingering Souls is probably your best play, but setting a battelfield for a planeswalker or an Olivia Voldaren is good too.
• Turn 4 and forwards try to put preassure onto the battlefield if it is safe (for example, if you know he/she may have a Lighting Bolt, save Olivia Voldaren for turn 6 so you can pay for the ability and put a +1/+1 counter on her) and take care of the big stuff with Terminate, Dreadbore, Cracklingg Doom and Path to Exile.

I built a semi budgget mana base. Since it's a 3 colours deck (you need lots of 2 colour lands) and you need to cover turns 1, 2 and 3 you can't afford to play offcurve with taplands. Checklands work good with Shocklands and Fastlands are the third best type of land in modern, but you need a Plains/Mountain/Swamp for Checklands so you can't run too many Fastlands. Pain lands are an option too, but in this deck (with shocklands, Night's Whisper and Painful Truths) painlands are too painful.

IMO the worst matchups are Burn and BW control decks, I haven't tested it enough to say tho. Sideboard can be greatly improved for those matchups (Kor Firewalker against burn for exemple) or other situations aswell.