Wannabe Breloom
Leftovers/Stead Fast
Impish/252HP/252attack
-Hypnosis
-Substitute
-Focus Punch
-Ice Punch/Night Slash/Stone Edge
Hypnosis puts an enemy sleep, forcing a free swap out. Then, you can substitute safely. Third move is STAB, and last move is coverage.
I love Sub-Punchers as much as the next guy, but Gallade is one you'd least expect. That said, you can catch so many people off guard with Hypno-Sub-Punch Gallade. They'll see Hypnosis and likely think you're a Status-spammer, only to get Focus Punched in the face.
Any Pokemon capable of Sub-piercing (Technician Cinccino, Icicle Spear-Cloyster, Dual Chop-Dragons, Bonemerang/Bone Rush-Marowak, and a few others) will have a good chance to ruin a Sub-Punch since Multi-hit Moves (like those mentioned) are Physical. Rock Blast is the least worrysome because of the bad matchup of Rock VS Fighting, so you have a slim chance to keep your Sub, even with Gallade's low HP. My mention of Rock Blast use reminded me of Garbodor, who has access to Acid Spray, and that got me thinking further...
Among potential Special options for countering Gallade, Acid Spray is one of the ones to worry about. Your Sp.Def getting halved in one hit ruins any Focus Sash potential (unlikely) and decreases Gallade's ability to Special Wall. Few Pokemon have the Sp.Atk to use Acid Spray properly, but Tentacruel, Accelgor, and Octillery have the best potential. However, all 3 have issues against Gallade's offense:
-Accel' fears getting hit in-general* and can only neutral-hit Gallade
-Octillery needs Trick Room to outrun Gallade, is easily handled by either Thunderpunch or Leaf Blade, and is only-slightly-less of a glass cannon than Rampardos
-'cruel has low Defense, slightly-above-average Sp.Atk, and is handled by either Thunderpunch or Bulldoze/EQ
-All 3 may only get a single shot in if they have to switch into Gallade
* Crunching the numbers, CB-Shadow Sneak is a rarely-3-mostly-2 KO (barring Giga Drain, Leftovers, Sitrus Berry, etc.) against an Accelgor with 31 IV, 4 EV HP and 31 IV, 0 EV Defense (those EVs are rather likely, given its high Base Speed and Sp.Atk stats). CB-Shadow Sneak is guaranteed to 2KO after a single Justified boost. Given Gallade's possibility for stronger Moves, you'll probably only see this matchup (if at all) when both are at the start of a battle.