DEOXYS
I'm pretty sure my first exposure to this Pokémon was the movie
Destiny Deoxys. I first watched it right around the time I had been playing my first game, Emerald, and boy did I watch it a
lot. It's arguably the Pokémon movie I've watched the most, and for that, it stands out to me more than the other movies, other than a few that include
Heroes and
Giratina & The Sky Warrior. I'm not sure why I watched it so much, but I really enjoyed it, and since I've recently acquired the Blu Ray, I figure I'll give it another watch one of these days.
I absolutely loved the Pokémon in that film, especially the main focuses Rayquaza and, of course, Deoxys. As a kid, Deoxys was awesome, but also really frightening and intimidating. The weird noise it made always freaked me out, as did its transformation sequences, and I was astounded by how absolutely powerful that thing was. Of what else I remember from that movie, the interaction of the two Deoxys was heartwarming. Sadly, I don't believe I have ever witnessed any of its other anime appearances, but going back and watching that movie will probably suffice for now.
I love its unique concept of being able to transform freely to many different forms that enormously change its stats, and I like the different appearances as well. My favorite form is Attack; it makes the best use of Deoxys' design elements in my opinion, and it's very competitively viable, although all of them are in their own right, especially with the help of such a varied movepool. I don't believe I've ever owned a Deoxys until that B2W2 event in early 2013. In my first playthrough of AS, I failed to catch the Deoxys in space. I may go back to Sky Pillar and try to catch it again. I already have one, but hey, the more the merrier I suppose.
Koffing
Not much for me to say on this one, but I definitely remember this one quite a bit growing up. One of the more iconic designs of Gen 1, and one of the most definitive designs and concepts for a Poison-type Pokémon. Not among my favorite Pokémon, or designs, but I think it's really good in its own right, and got a good, long spotlight in being James' primary Pokémon for the first three generations, and since I'm sure there's only a slight possibility that Weezing will end up as a POTD, I'll just say it here- James releasing his Weezing (along with Jessie and her Arbok) is among the most simultaneously heartwarming and tearjerking moments of the show, and the episode was one of the best that featured Team Rocket. I am honestly hoping that one day, we'll get to see Arbok and Weezing, along with their pre-evolved counterparts they took care of, again one day. It's been 13 years, it gets more doubtful every year, and I'm not expecting it to happen, but I'd love for it to.
I don't remember ever using a Koffing myself, actually. This guy, and his older brother, is quite a bulky nuisance in NU, though.
Wailord
I probably did use this mammoth once or twice before, but I honestly don't remember much. What I do remember is learning about it being the largest Pokémon in existence in elementary school way back then, and it had a bit of a reputation for it. If anything, I'm really impressed with the sheer size they gave this guy. I don't really breed often, and I don't think I ever tried breeding a Wailord and Skitty, but I think I will one day for the novelty of it. Best case scenario, a baby Wailord will learn Double-Edge from its father Skitty, and a baby Skitty learns nothing from its father Wailord, so there's not really any egg moves that interest me here. As for the Wailord/Relicanth Regi puzzle, I did that for the first time in AS last month or so, and I most definitely needed to look that up, haha. I even caught one of each to do that. Never hurts to fill up the Dex, as well.
Mr. Mime
Undoubtedly one of the most oddly-designed Pokémon, and one who went through self-contradiction from the introduction of the gender mechanic, Mr. Mime is definitely one of the most interesting Pokémon in my opinion. It's really high in the list of out-there, oddball Gen 1 designs with Jynx, to me, and is also a mon I don't really think about too much in the modern games or anime because I rarely ever see them in there these days. I don't really think that adding a Fairy typing was fitting for Mr. Mime, (or the Granbull line), but eh, it's nothing that awful. At the least, it's nice to see it get some modern-day attention in the form of new feature additions, even if it's not a Mega. I certainly don't remember ever using this guy, although I possibly used Mime Jr. once or twice in Diamond/Platinum.
Pachirisu
One of the Pokémon I think I remember most from Gen 4. It's got a cute design (arguably the most unique of all regional electric rodents), and I specifically remember Dawn's mischievous Pachirisu in the DP series of the anime, particularly the episode in which she catches it.
Its old cry was one of the ones that I felt that they butchered in
Gen 6, sadly. I was a little upset to eventually learn its competitive viability was under average, but it kinda makes me happy that it was an underdog at Worlds a couple years ago. I've used one here and there throughout Gen 4, and I may start doing it again in 6 eventually.
Pachi's not on my list of all-time favorites, but I do have a good amount of respect for it. As for all of the regional electric rodents, I'd say it ranks pretty high. I think Pichu may be my ultimate favorite, and Emolga definitely in last. Will avoid going into detail here but while it's pretty cute, the Volt Switching Emolga used by Elesa are among the few things I remember vividly about Black and White...Clemont's thankfully wasn't as annoying.