Gallade is certainly popular; most of his sets were already mentioned before I got here. Popular or no, though, he has a lot of competition for a fighting-type Mega, so weigh the advantages and disadvantages for your particular team carefully. One OO I'd like to mention: Adamant nature. An Adamant +2 Drain Punch is a huge nuisance, especially to some stall tactics. On a side note, the game's AI for the Maison fares terribly against this option.
As for standard Gallade, you'll mostly see sets similar to its Mega, but it does have a bulky set too:
Unlimited Gallade Works (sorry)
EVs/Nature: 248 HP / 252 SpD / 8 Spe, Adamant/Jolly nature
- Bulk Up
- Drain Punch
- Knock Off
- Substitute / Zen Headbutt
This set relies on boosting slowly and healing with a gradually more powerful Drain Punch as you go. Your best shot is tonswitch this into something that is oriented toward Special attacks but can't set up easily, or something you can handle via Substitute. Knock Off gets good coverage alongside Drain Punch and removes the foe's item, always useful. in the last slot, Substitute is probably more useful since it absorbs status and other annoyances, but Zen Headbutt can be used if you're worried about fairies and want another STAB. This set is designed for lower tiers, though, so don't expect much from it in more inclusive formats.
The risk I took was calculated, but man, am I bad at math.