Just to clarify, this is for OU, not Ubers. If something made the jump to Ubers (Salamence in DPP, for instance), it can still be considered for the OU presence it had. Also, we're just nominating mons for now, so if something is already nominated, there's no need to repeat it; it'll be in the pool.
Gonna take this moment to nominate Jolteon. JoltWak was solid in GSC, Jolt was a great BPer in ADV, and GyaraJolt was quite effective in DPP. While it was never the most dominant force in those metas, it was consistently a strong presence and might crack the top 10 for overall~