Here you go. A game starring Waluigi, just like you wanted. True, it's not an official game by Nintendo, but as far as quality goes, it's pretty damn close. Note that I'm just going to link to the TV Tropes page. You can decide from there if it's something you'd like to check out for yourself, or just stop at that point. There should be a link to the actual game on the page for anybody interested
http://tvtropes.org/pmwiki/pmwiki.php/VideoGame/PsychoWaluigi
It's a personal favorite of mine. Kind of "Mario-meets-Kirby" as far as gameplay goes. I mean, you have Mario-style physics, enemies, environments, etc., but Waluigi's special skills feel quite similar to Kirby. For instance, you can grab a Snifit and hold it to where the bullets that it's shooting will hit enemies instead of you, with full control over when it shoots. Once it's out of ammo, you just throw it away (possibly hitting another enemy with it and taking them both out), and grab something else. If you don't want to do that, you can always just stomp your enemies like any other Mario game.
Like I said, not an official game, but considering Waluigi's in your number-1 spot, this seems like something you'd probably enjoy quite a bit.
