Glaceon

Glaceon is one of the three welcomed Gen 4 additions to the Ice-type family. Despite Glaceon learning the best possible Ice-type moveset, Mamoswine still wins by having better stats. That said, it's still a great Pokemon. Like all Eeveelutions, Glaceon benefits from Eevee being common, especially in places where Swinub are rare.

Best PvE Offensive Moveset

• Frost Breath and Avalanche are among the best Ice moves.
• Ice Shard is pretty close to Frost Breath on offense.
• Ice Beam is a good move, but is strictly inferior to Avalanche.
• Icy Wind is just bad.
• Last Resort isn't meant for attacking gyms or raids. 
• Water Pulse doesn't have any use for Glaceon offensively. 

Best PvE Defensive Moveset

• Ice Shard hits harder than Frost Breath on defense, but they are close.
• Water Pulse is the most favorable move for defense due to its useful coverage against Glaceon's weaknesses. 
• Avalanche is a powerful 2-bar move that’s strictly superior to Ice Beam.
• Icy Wind is 3-bar move, but it’s weak and very easy to dodge.
• Last Resort as a 2-bar move offers some neutral coverage, but is easily dodged. 

Glaceon has similar issues to Leafeon, which is the lack of adequate coverage among its movesets. Ice Shard deals slightly less damage than Frost Breath, but returns more energy.

Icy Wind is recommended for its debuff utility on the opponent, in addition to its lesser energy cost and STAB damage. Avalanche can be chosen for much stronger damage, but doesn't provide any extra coverage. Last Resort and Water Pulse can only be obtained from Community Day events or Elite TMs, but are somewhat poor moves for coverage. The latter is more favorable due to its coverage against Fire and Rock Pokemon, as well as not being resisted by common Steel Pokemon. Ice Beam falls behind other moves in terms of performance.