Gligar

Type Tier
Ground / Flying UU
Statistics
Stat
HP
65
333
Atk
75
248
Def
105
308
SpA
35
168
SpD
65
228
Spe
85
268
Name Item

Screecher

Leftovers
Moveset
~ Screech
~ Earthquake
~ Wing Attack
~ Counter

Screech on the switch, and if you've got a shot at taking them out, go ahead. You're not going to be able to touch Zapdos or Skarmory, but then again, with Counter, they're not going to do too much to you without getting killed. With his decent Defense, Counter is also great for Snorlax and Marowak.

Name Item

Thief

Mint Berry / Miracle Berry / None
Moveset
~ Earthquake
~ Wing Attack
~ Rest / Protect
~ Thief

Only use Rest with Mint Berry. This is the old "standard" Gligar. Ideal if you can steal a Thick Club from Marowak or Leftovers from Snorlax/Zapdos.

Other Options

If you're really desperate to hit Zapdos, there's Sludge Bomb and Hidden Power Rock. You could just put Sludge Bomb over Wing Attack since you're not going to touch Skarmory anyway and Heracross isn't seen as much recently. Gligar can Curse instead of Screech, but I don't know if he has the kind of time for that.

Opinion

A good concept Pokémon (Ground and Flying cover each other pretty decently), but torn to pieces by mediocre stats and bad movepool. He does make a decent underused counter to Marowak and Raikou, but that's about it.

Counters

Most Water-types that have even a minimal semblance of stability can take on Gligar with Surf or Ice Beam; among those ranks are Suicune, Slowbro, Starmie, Quagsire, etc. Flying-types also work well with their immunity to Ground, especially special based ones like Moltres and Articuno. Zapdos and Skarmory beat Gligar through attrition, as they resist Wing Attack as well.