Forretress

Forretress finds a secure spot on many OU teams due to its ability to viably compress Rapid Spin and Spikes support. It also has excellent physical bulk and a fantastic Steel / Bug defensive typing that gives it useful resistances to Psychic-, Ice-, and Normal-type moves and an immunity to Toxic, which allows it to switch in and set up Spikes and use Rapid Spin on passive Pokemon with Toxic like Umbreon and Skarmory. Its resistance to Normal-type moves also allows it to tank Explosion and Self-Destruct from the likes of Steelix and Snorlax, making it a good choice to attempt to take those moves aimed at key teammates after Forretress has set up Spikes. However, Forretress has the lowest Special Defense of any fully evolved Steel-type, meaning that it can often be overwhelmed by strong special attacks. Forretress also has a terrible 4x weakness to Fire, and its poor Special Defense and the popularity of Steel-types as a whole mean that it has a tendency to be lured in and KOed by Pokemon it would usually set up on, such as Hidden Power Fire Exeggutor and Fire Blast Snorlax. Finally, Forretress faces competition as a Spikes setter and Rapid Spin user from Cloyster, which is much faster, has a more threatening Explosion due to its higher Attack stat, and has STAB Surf, which allows it to offensively pressure all Explosion-resistant, physically defensive Pokemon, something that Forretress struggles to do with its pathetic Special Attack and bare offensive movepool. However, Forretress's lack of weaknesses outside of Fire means that it can choose to risk a strong neutral or resisted hit in exchange for setting up or removing Spikes against a wider pool of Pokemon, such as Nidoking and even Raikou and Zapdos. The strategy of wearing down Cloyster with Toxic that stall teams often use will also be ineffective against Forretress, making it a useful pick when trying to outlast them. Lastly, while Cloyster must drop a key move in Explosion in order to run Rapid Spin, Forretress is free to use both on the same set.