Leafeon can be used as a physical sweeper or a wall/cleric:
Lefeon @ Life Orb
Chlorophyll
Adamant Nature
252 Attack/84 Speed/168 HP/4 Sp. Def
- Leaf Blade
- Knock Off
- X-Scissor/Sunny Day
- Swords Dance
Whether you use Sunny Day or X-Scissor depends on if you have Drought/a supporter with Sunny Day or not. 84 Speed EVs is to make sure you outspeed Scarfed/+1 base 100 Speed Pokémon (at Lv. 50). Everything else is thrown in HP for extra bulk except for 4 EVs in Sp. Def to get an odd HP number.
Leafeon @ Lefovers
Leaf Guard
Impish or Bold Nature
252 HP/252 Def/4 Attack or Sp. Attack
- Giga Drain/Leaf Blade/Knock Off
- Synthesis/Wish
- Protect
- Toxic/Heal Bell
Straightforward set. If you want to use Giga Drain then get Calm Nature, Leafeon's Attack is (much) higher than it's Sp. Attack so Impsh with Leaf Blade (STAB) or Knock Off (utility) might be your preferred option. Synthesis gives you immediate recovery and is boosted to 75% if under the sun, but keep in mind that it heals only 25% under rain, sandstorm or hail. Wish heals 50% HP consistently and works well when paired up with Protect; it can also be used to heal injured allies. The last slot you can use Toxic for some stalling or Heal Bell for support.