1. Wolf - Seriously? I mean, really? Look, I'm all for roster diversity, but they could have at least added a character from the Star Fox series that has been a long-standing contributor. Why not Peppy or Slippy? Hell, even Krystal makes more sense and I hate her.
First of all, I love your nick... but anyway...
Wolf makes perfect sense, being in every game but the original SNES game and Adventures (which wasn't a Star Fox game to begin with...), and Fox' rival. In fact, he makes more sense than a whiny mechanic or an old man or a character who only has been added in the later half of the series and doesn't do much but wobbling her boobs.
2. Pichu - Removing him from the Smash Bros. roster was perhaps one of Sakurai's most intelligent decisions. A clone of Pikachu that is worse in every way and hurts itself? And on top of that, I'm not sure I support the idea of adding any more Pokemon to the game. The game is flooded with them as it is, which brings us to...
Pichu was intended to be bad. He was a joke character. That concept isn't new. Just like with women being introduced to fighting games by that series first, Street Fighter was the one that came up with joke fighters that were bad on purpose. Maybe Dan Hibiki rings a bell, should you be familiar with the series. Pichu also represented the Pokemon generation that was current back at Melee's release, which was the second generation.
3. Lucario - I know that furries enjoy killing people with this guy over wifi (no, seriously, you're not good at the game), but he is probably the worst addition to the series ever. He was in a poor anime movie (what anime isn't poor, though?). Mewtwo was iconic to Pokemon and he was removed, but this loser was put in his place? Um.
Lucario's addition has nothing to do with furries, and, by the way, there are very good and respected players here on SWF that also are furries. And not every Lucario player is bad, and neither every Lucario player is a furry. I love how people on the internet take every opportunity to bash furries. It's getting annoying.
But Lucario was mainly added for representing the current, 4th Pokemon generation, for which he is the icon and most popular Pokemon (I haven't followed the series at all since the first generation and even know this guy myself, so that says something).
Mewtwo, by the way, was replaced by Sonic. Not Lucario.
4. Toon Link - Do I even have to explain this one? It's Link, in toon form! Some compelling ish that is.
Toon Link stands for what Young Link stood for in Melee: The "young"/toon subseries of the Zelda games. Sakurai himself stated the importance of two Links in Smash Bros., if I recall correctly. There are several timelines in the Zelda series, and the Toon subseries has currently more games than the "mature" one. Going from Ocarina of Time that started the whole timeline split, only Twilight Princess follows the story of older Link, while every other game follows the younger Link's story. Not too sure about the GBA games.
5. Ice Climbers - 100% agree with the OP. When the Ice Climbers were announced as a playable character in SSBM, I had to Google Search them to figure out who the hell they were. There are dozens of iconic Nintendo characters that are instantly recognizable, even old school ones (Pit, for instance) and we get these clowns. Nice.
I almost cried in happiness and nostalgia when I saw the Ice Climbers in Melee. Besides, they add a very interesting gameplay style to the Smash series: a character compelled of two characters with the same moveset simultaneously in the fight. This is a mechanic that Smash hasn't seen in any other form so far. Not to mention that Sakurai likes them. I think they are a great addition to the roster.
I love how almost nobody mentions Roy. I mean, he was in there for advertisment for a game that was only released in Japan... Oh right, he has t3h ph1r3 and is from a "cool" series. Of course. How could I forget that. I can see why he was put in but I think the choice of him was pretty unnecessary in the first place. So... Roy is imo the only character who never should've been in Smash.
Other than that, I am pretty content with every game's roster and think the choices are clear and understandable by the point of view from a developer in Japan, and not a Western gamer who grinds his ***** over Twilight Princess and Final Fantasy.