Included in this crowd are a dog, a zombie construct, and at least one lesbian.
Yes, yes, we all know Girl on Girl Is Hot. But what some authors are only just beginning to realize is that, for a growing number of women (and of course, men) Guy On Guy Is Hot. While not a ubiquitous cultural assumption in Real Life the way its Sister Trope is, it is nevertheless an existing mentality. It's the reason for the Boys Love Genre, and the times when Ho Yay is played intentionally for Fetish Fuel. Some authors adhere to this, or at least acknowledge its existence, and thus we get scenes of naked and half-naked menwrestling in either mud or jello.
In fiction, this philosophy may be treated in-universe as a full-on Spear Counterpart to Girl on Girl Is Hot, with the assumption being that it's normal for women to ogle gay men in the same way that straight men are assumed to enjoy lesbian action.
Just as often, though, there is a heavy Double Standard; straight men thinking Girl On Girl Is Hot will be taken for granted, whereas the female enjoyment of Guy-on-Guy will be treated as a perversion (See Yaoi Fangirl). Or, in the other direction, female characters will proudly declare their fascination with gay guys doing it while denouncing men who eroticise lesbians as exploitative perverts.
There's often an element of But Not Too Gay to this trope: women may enjoy watching men wrestle or cuddle, but unlike men in the reverse scenario it may be implied that they wouldn't actually find it sexy if the situation were to "escalate".
This trope is a large part of Axis Powers Hetalia's raison d'être. France spends most of his time stripping and/or groping the other male characters, Italy has a habit of glomping or sleeping with Germany while naked, and the series even has its own resident Yaoi Fangirl, Hungary.
Konohamaru's Sexy No Jutsu had two shadow clones transform into a nude Sasuke and Sai locked in a very suggestive pose. It got cut in the anime, but the manga version can be seen here. It even gave Sakura a nosebleed.
In the English print of this manga scene, the male on male part was nearly blacked out entirely, while the girl on girl scene only needed a few extra clouds to censor naughty bits. Major Double Standard on VIZ's part. Remember kids; getting the hots for naked ladies together is okay, but you're not allowed to even look at two guys. EVER!
There's also the infamous accidental kiss between Naruto and Sasuke. You could almost hear the simultaneous clacking of one thousand fangirls typing one thousand Slash Fics at the same time.
For once played for drama in Ooku. When Shogun Tsunayoshi is developing God Save Us from the Queen! tendencies, she orders two of her male concubines to have sex for her entertainment, thinking they won't mind since she knows them to be lovers. They're so insulted at being used for voyeuristic thrills that they commit seppuku, giving her a salutory shock.
This is Hikaru and Kaoru's entire schtick in Ouran High School Host Club, with the twincest angle to spice things up. And it's never entirely clear if it's just an act or not.
In Get Smart, when Max appears to be humping a male Control agent (he's actually trying to pull him off the table), a guard, in a rare male example, walks by and looks a little too interested before being pulled away.
In The Princess Diaries 2 (which is a Disney movie aimed at pre-teen girls, just so we're clear), there is a scene where Mia and her best friend Lilly are looking at prospective princes. Mia remarks that one prince shown is cute, to which her bodyguard Joseph replies, "His boyfriend thinks he's handsome also." Mia and Lilly's reaction is ... enthusiastic.
Rita: Is there a girl you're seein'? Bobby: Seein'? Uh I see a lot of girls...I see I lot of guys too.
Rita: I think that's sexy, you ever been with a guy and a girl at the same time?
In Run Fat Boy Run, Dennis and Gordon oversleep and have to race to the marathon in a cab, Dennis thrashing around trying to get dressed as they go. When they stop at a traffic light, they notice there's a woman looking into the cab at Dennis in his pants straddling Gordon... and she seems to be enjoying the show.
Anita Blake. Two guys together gets Anita and Belle Morte off.
Buffy the Vampire Slayer gets annoyed with the mutual jealousy of her two vampire ex-boyfriends and suggests putting them in a room together and having them wrestle it out. When Spike says it's fine with him, her eyes widen with excitement and she adds, "There could be oil involved." Note that this trope is a view held by much of the show's fanbase as well.
There was a skit on The Chris Rock Show where two men cross paths on the street and it looks like they're about to fight... and they make out instead. All you can hear from the audience is women squeeing. You can watch it here (even if the end was just spoiled out of necessity). While hilarious, the clip is sadly a case of artistic license, as racial bias and tension have long been a sore point in the gay community.
Doctor Who, "The Doctor's Daughter" - Jenny kisses a guard through the cell bars so she can grab his gun.
Donna: (to the Doctor) I'd like to see you try that.
In the Farscape episode "Won't Get Fooled Again", one of the many crazy scenes involves a Camp Gay D'Argo propositioning John. Apparently Chiana wants to watch...
In one Friends episode, Rachel had an Erotic Dream that featured Chandler. Later, it also included Joey, then Rachel mentions that sometimes it was just Chandler and Joey. The guys leer until they realise what that means.
One of the Patients of the Week on Grey's Anatomy was a gay soldier. Once his boyfriend comes to visit him they are alone and proceed to make out. Meredith Grey walks by, and stares at them with much interest.
Noah's Arc: Brandy finds two guys together quite sexy, though overall the trope goes without saying for the LGBT genre (at least on the male end).
A meta-example: Queer as Folk was a show about gay men and their relationships and sex lives. Its primary audience was meant to be gay/bi men and, to a lesser extent, lesbians. Yet it gained a huge fanbase among straight women.
Saturday Night Live has a recurring skit called the "Kissing Family" which features a considerable amount of intense guy-on-guy kissing. Inevitably there will be squeals of delight which overpower the laughter.
Jordan: We should have sex later. Dr Cox: (unnerved) How did you get from that image to that thought?
There was an episode of Sex and the City where the girls rent gay porn for this reason and watch it together.
State of Play. A homosexual member of the newsroom mentions he just slept with the man they've been investigating. When he asks if they want him to go into detail the men immediately say "No!" while the female journalists have exactly the opposite response.
In Shadow Hearts: Covenant, after you beat The Great Gama in Joachim's sidequest, he passes on his abilities to Joachim by engaging in some off-screen gay sex with him in the wrestling ring right in front of the whole party. While Juri isn't especially thrilled to see this, Anastasia comments that she finds it "beautiful".
In order to force Ethan to get together with a guy who previously called him out on his jerkish behaviour, Robin adds a clause to the anti-cancer bill she's trying to get through Congress that will force the two to make out at least once a week. As soon as she does, the bill gains significant support among women.
Amber repeatedly expresses enthusiasm for anything which results in two dudes getting it on.
In Skin Horse, Tip and Konstantin mud-wrestling attracts quite an audience, including a Kinsey-Sevennote For those just joining us at home, the Kinsey Scale runs 0-6, with 0 being perfectly heterosexual and 6 being perfectly homosexual lesbian and a sapient swarm of bees.
Sticky Dilly Buns, a spin-off from Ménage à 3 (see above), features the naive, virginal Ruby, who is doomed to a rapid education in life, including, early on, exposure to the sight of two gay guys having sex. She subsequently suffers flashbacks to the scene, and can't disguise the fact that she found at least one of them very good-looking.