Tuomas has been paired up with every other man in the band. In all fairness, he DOES make a really lovely and cuteUke.
Brendon Urie. He's generally characterized as so sweet and loving and openhearted and completely faily, it's hard not to pair him with anyone. Especially anyone male. In fairness, this◊, this◊, and this◊ would just be wasted otherwise.
The disputed rumored bisexuality of John Lennon has made him the focus (and fan bicycle) of about 99.9% of slashy fanfiction in the squickier areas of the Beatles fandom.
Miley Cyrus has been paired with everyone who has shared a photo with her and possibly some who haven't.
Subverted and played straight with Patrick Stump. Subverted in the slash end of bandom in that he's paired with Pete Wentz 95% of the time, played straight in that in het circles, he's paired with nearly every female in the bandom scene with any level of significance (even the ex of the guy he's paired up with the most)
On the other hand, Pete Wentz is arguably the de facto bandom slash shipping bicycle.
Len is no slacker, either...he's been paired with Lui, Gakupo, Kaito, Miku, Rin, Gumi, Teto, Ia, Neru, Lenka...and those are only the ones this troper can think of off the top of their head. Though, Vocaloid being itself, everyone is this trope. Everyone. Up to and including Yuki, who has been shipped with seven different characters. This isn't much for Vocaloid, except that Yuki is nine.