All those times trying to catch a non evolving pokemon. Especially in the earlier games. Took around 5 tries and 50 balls of varying level to catch a level 10 Heracross in Pokemon Silver, 30+balls on Stantlers, Girafarigs and Yanmas. I expect this sort of behaviour with legendaries but these things are not so and therefore should be easier to catch.
Murkrow in my diamond was also a prat... luckily that exact scenario led to me finding a shiny Buneary so all good in the end I guess.
Over 9000 balls on Beldum. Don't even go there with Beldum... just transfer the free one you get in gen 3 and get it busy with Ditto.