I've been using the following two decks a lot in Arena 7, pushing Legendary.
Deck 1:
Giant Lvl 6
Barbs Lvl 9
Archers Lvl 8
Arrows Lvl 8
Lightning Lvl 3
Goblins Lvl 9
Spear Gobs Lvl 9
Skeletons Lvl 8
Avg Elixir: 3.4
All low-level cards for the most part, using the Giant starting at the back of my base and then throwing a ton of excess troops to both lanes once he crosses one bridge. No flying troops at all. Biggest weakness is a high-level balloon which can usually hurt a tower badly before my ground-to-air troops take it down.
I find this works really well. Barbs, Skeletons, Arrows, and Lightning are all used defensively. Lightning in particular is awesome for taking out towers. Offense is Giant, Archers, Gobs and Spear Gobs.
Deck 2:
P.E.K.K.A. Lvl 3
Three Musketeers Lvl 5
Minion Horde Lvl 8
Zap Lvl 8
Lightning Lvl 3
Barbs Lvl 9
Elixir Collector Lvl 5
Wizard Lvl 5
Avg Elixir: 5.5
This is a specific deck I'm still building up. Would like to swap the Wizard for the Ice Guy but he hasn't dropped yet. Need to get the Musketeers to Lvl 6 to make the rapid attack work perfectly.
Main attack is PEKKA from back of base, add 3 Musketeers + Wizard behind him in a single lane once he reaches the bridge. Can waste a tower in seconds. I've tried swapping the Wizard for my level 9 Bomber, but I find the Wizard is a bit better in the role of protecting the PEKKA and Musketeers (his only real role is support).
Barbs, Minion Horde, Zap, Lightning, and Elixir are all defensive. Placing Elixir in front of the Castle for defense as well.