Do you ever just catch a pokémon you randomly encounter for various reasons? For example, I just caught a wingull as I was heading to my secret base to train leafeon. I thought it was just such an interesting spot (it literally was under the waterfall I have to climb and I was going slow enough it bumped into me). So I thought it'd be interesting to toss the pokéball (as I do) to see if it just wanted to join me. No resistance and it joined my team (had one spot open). Interestingly, it happens to have twister, so not just any old wingull!
I've also, in the past mostly, been impressed when a 'mon I'd fight would withstand an attack where others with similar level I believe fainted or was faster where others couldn't keep up. What about you?