Shadow Watchog

Watchog is like the Gen 5 version of Raticate, which is rather unfortunate. Pitiful stats, incompatible movesets, and a sub-optimal typing for the meta makes Watchog pretty useless for anything. 

Best PvE Offensive Moveset

• Bite is the superior move stat-wise, and pairs with Crunch to fulfill a Dark-type role. 
• Low Kick performs very similarly, but doesn't synergize with Watchog's charge moves.
• Hyper Fang takes advantage of STAB to out-perform other options, but can't be Super Effective.
• Grass Knot is a good move, but isn't really meaningful for Watchog. 

Best PvE Defensive Moveset

• Low Kick and Bite both perform poorly on defense, but the latter is less preferable due to the likelyhood of Fighting-types used to attack Watchog. 
• Crunch is the hardest to dodge and is also a 3-bar move, but it's also most likely to be resisted by Fighting-type counters.
• Hyper Fang offers neutral coverage and does good damage with STAB. 
• Grass Knot is the slowest on defense and doesn't provide meaningful coverage. 

Bite + Any

Bite is superior to Low Kick in performance, though it has poor energy generation. 

Crunch is a bit redundant with Bite, but requiring less energy than other options makes it more accessible and also lets Watchog wall most Ghost-types. Hyper Fang takes advantage of STAB to provide decent neutral coverage, though it can't be Super Effective against anything either. Grass Knot hits hard and provides coverage against common Water Pokemon.