Pre-evolutions easily found in any cave, 130 speed, non-legendary, Poison-flying type, not a wall. It does share the ice weakness with Garchomp but it is 4x resistant to Umbreon's weaknesses and the rest of Crobat's weaknesses are resisted or immunized by Garchomp(Immune Electric resists Rock) and Umbreon(Immune to Psychic). Crobat has a nice base 90 Attack and Acrobatics for strong offense, he can also use Nasty-plot to boost S.Attack. As for flinching moves he has: Zen-headbutt, Bite, Twister, and Air-slash.
Magikarp are everywhere!AHHHHHH! boostable 81 speed with dragon-dance, non-legendary, Water Flying type, not a wall. It does not share any weaknesses with the others and his two weaknesses are deal with by Garchomp(Electric and Rock), he also resists Umbreon's weaknesses. Great Attack at base 125 that is further boosted by D-dance. He has Waterfall and Ice-fang for flinching.
Staryu is pretty easy to find and evolve into Starmie, Great 115 Speed, non-legendary, Water-Psychic, not a wall. Does share bug weakness with Umbreon but resists Garchomp's Ice weakness and Umbreon's Fighting weakness. Good special attack and large movepool. Only has twister and waterfall for flinching so I would not use it for that, but it is a very good sweeper and/or Spinner.