Fuck yeah! I love Double Battles! Much more room for creative strategy than its Single kin. I've taken up pages of my school notebook creating Double Battle pairings, but I'll only put a few up at a time:
Heatran+Swampert/Empoleon (late game sweep)
Heatran @ Expert Belt
Flash Fire
4 HP/252 Special Attack/252 Speed and Naive
-Heat Wave
-Earth Power
-Explosion
-Protect
Swampert @ Leftovers
Torrent
240 HP/216 Defense/52 Special Attack and Relaxed
-Earth Power/Earthquake
-Ice Beam
-Surf
-Protect
Empoleon @ Petaya Berry
12 HP/252 Special Attack/12 Special Defense/232 Speed and Modest
-Agility
-Substitute
-Surf
-Ice Beam
There are a few things I do with this team:
1- If Heatran is with Empoleon, Empoleon uses Agility to assure that he is faster than Heatran, so a Sub can be put up if Heatran decides to kill everybody with Explosion, while Heatran takes out any threats. Chances are, the universal resistance coverage will force a switch, having one of Heatran's attacks damage an incomin Pokemon, and Empoleon getting a free Agility. Empoleon then puts up a Sub while Heatran either takes out whatever switches in, or Protects from an EQ. If the pressure's on Heatran, Empoleon will Surf, and if it's on Empoleon, he'll Sub again. This continues until Empoleon is in Torrent+Petaya range, and then a sweep commences.
2- If Heatran is with Swampert, I will either start out with an appropriate Protect+ combo (Protect+Surf if Heatran is in danger, and Protect+Heat Wave/Explosion/Earth Power if Swampert is in danger). If I don't suspect that either is in danger, or if I feel a switch coming on, I'll use the appropriate moves. Most people don't expect me to have Protect on Heatran (assuming it's Scarfed or Spec'd), and consequently, don't expect Surf to be used, or for Heatran to switch out with a Flying type if EQ is imminent. The advantage over a physical Swampert is better Water/Ice attacks, and not having to use EQ.
Aerodactyl+Togekiss (suicide lead/flinch)
Aerodactyl @ Focus Sash
Pressure
252 Attack/252 Speed/4 Defense and Adamant
-Taunt
-Stealth Rock
-Earthquake
-Rock Slide
Togekiss @ Leftovers
Serene Grace
252 HP/252 Special Defense/4 Defense
-Thunder Wave (thinking of changing to Tri Attack)
-Air Slash
-Heat Wave
-Aura Sphere
Aerodactyl is mostly out there as a suicide lead, to Taunt anyone planning on crippling someone with a status or setting up, or setting up Stealth Rock if Taunting isn't necessary. Focus Sash is there so I can get either Taunt and Stealth Rock, or Stealth Rock and Rock Slide/Earthquake. Rock Slide over Stone Edge because Stone Edge is the worst move in the game, Rock Slide hits both opponents, and Earthquake to get rid of frail Electrics or put a dent in some Rock/Steel types.
Togekiss usually starts off with Thunder Wave (which I'm planning on switching with Tri Attack for STAB, offensive, and chance to freeze, paralyze, or burn), and if I feel an Electivire switching in, I Earthquake with Aerodactyl. Air Slash is there for hax Flinching, Heat Wave to cover fucking Scizor or Forretress, and Aura Sphere there because I like it. I might switch it in with Nasty Plot, because Heat Wave covers most things Aura Sphere does, or Roost to eliminate Rock, Ice, and Electric weaknesses while healing.
The main idea here is to set up with Aerodactyl while Togekiss paralyzes, and then go flinch-crazy with Air Slash and Rock Slide. Earthquake doesn't affect Togekiss and puts a dent in dangerous Electric types, which can usually be taken out with Heat Wave. They both have moves that damage both opponents, which is handy in Double Battles.
That's all I have time for now, I'll put some more up later. Feel free to tell me where I've screwed up!