Best gimmick?
Swoobat
Simple, Calm, Salac Berry
Substitute
Calm Mind
Stored Power
HP Fire/Fighting
Put up sub on predicted status or if youre faster. Simple boosts all stat boosts x2, so Calm Mind is +2 in each stat. Salac berry boosts speed at 25% HP, which Simple makes +2. I usually tried to get to +4 Sp Att/Def and +2 Speed and then wreck everything with Stored Power. HP purely for coverage.
Ive swept entire teams in lower tiers, but even Simple Sub Salac Swoobat just doesnt hold up in OU (and I tried, A LOT)
Honorable Mention:
Drifblim
Unburden, Calm/Bold, Weakness Policy
Will O Wisp
Stockpile
Ominous Wind
Baton Pass
Another set thriving on other trainers having no clue what youre up to. Stockpile/WOW at first to help make sure you live through an attack. Hopefully they activate your Weakness Policy trap card, that's kinda important. Unburden doubles your speed after item consumption without letting your opponent know, so after the hit get a sneaky revenge kill with Ominous Wind (which has a chance to boost all stats +1, just for extra shits n gigs) or ensure your Baton Pass. Drifblim becomes a one-time-use one-trick-pony, but its probably my favorite strategy for breaking the monotony of OU The Team: The Movie: The Experience.