Glalie has often been shunned as a Pokemon since its competitive debut. It's average at both offense and defense, and it has a very limited movepool. The creation of its evolutionary partner, Froslass, meant that Glalie was forced to reside in the dank, overcrowded recesses of the NU tier. However, with Froslass banished to the Borderline tier for the remainder of the DPP generation, Glalie finally has a comfortable niche in the Underused tier.
Glalie makes an excellent lead thanks to its above-average Speed, Taunt, and the ability to lay down Spikes. With decent stats, Glalie fits comfortably into many different types of teams. Taunt prevents slower leads from setting up their own entry hazards, and also stops opposing Taunt leads from ruining your fun. Glalie can then reliably set up multiple layers of Spikes before using Explosion to take a chunk out of one of your opponent's Pokemon. Leads like Uxie, Ambipom (thanks to Inner Focus), Mesprit, Spiritomb, and Omastar are all setup fodder for Glalie if you play it right. Ice Shard's primary purpose is to consistently break Focus Sashes, regardless of what lead you are up against, unless you're facing a faster priority lead like Pinsir.Team Options & Additional Comments >>>
Lead Glalie can run a set with a specially offensive spread and Ice Beam in place of Ice Shard, but the loss of power from Explosion is a real letdown. Crunch is also a possible option over Ice Shard if you feel that Alakazam and bulky Psychic-type leads are a problem. Ice Fang is a more powerful attack than Ice Shard, but it doesn't OHKO or 2HKO anything of note, so Ice Shard is generally superior for breaking Focus Sashes. Super Fang is plausible if you want to take chunks out of bulky Steel-type leads like Steelix and Registeel, but otherwise it's rather lackluster. Light Screen is an option to make Spiking easier, but Glalie is usually better served by using that moveslot for Taunt or Explosion.
Aside from the Lead set, Glalie's options are few and far between. A Choice Band set is viable, due to Glalie's access to STAB priority and Explosion. However, Glalie has a rather lackluster movepool and weak stats, as well as a weakness to Stealth Rock, leaving it utterly outclassed by Pokemon like Kabutops, Qwilfish, and Regirock. In the same vein, Choice Specs is also plausible, with Explosion to punish special walls like Chansey, but again, there are better Pokemon for the job.
On the defensive and support side, Glalie can run a bulkier Spikes set, but it is generally outclassed in that role by Qwilfish and Omastar, thanks to their superior typing, lack of Stealth Rock weakness, and access to more types of entry hazards. Glalie can also work in a hail team to make use of Ice Body, but Walrein outclasses Glalie for this role. Lastly, Glalie can run Sing from Pokemon XD; however, its shaky accuracy makes it very risky.
Checks and Counters
Glalie hates dealing with Arcanine and Kabutops when in the lead position. Both of them can hit Glalie with a super effective STAB move, and then follow up with priority, meaning that the most you can do is either throw out a single layer of Spikes or Taunt Kabutops to prevent Stealth Rock. Moltres also poses problems for Glalie, as it is faster than Glalie and can 2HKO with Flamethrower, forcing Glalie to set up only a single layer of Spikes. Leads with U-turn, such as Scyther and Swellow, are also an irritation for Glalie because they can break its Focus Sash, leaving Glalie open for a faster sweeper to come in and finish it off.