There are currently 252 games listed on the Visual Novel Database with the tag 'Seme Protagonist'. The generally held belief is that Boys Love is primarily played by cisgender women imagining themselves in the protagonist role, which perhaps makes it surprising that this 'Seme Protagonist' category actually has a higher count than the 'Uke Protagonist' tag. Boys Love, as always, is extremely psychosexually complex!

Here is a brief rundown of a few of the games where you can penetrate the love interests. 

Absolute Obedience - Zettai Fukuju Meirei by Langmoar is one of the earliest BL games to ever be translated into English. The game is extremely sexually extensive, with a huge cast of characters engaging in a wide variety of sexual roles and couplings.

Shingakkou -Noli me tangere- from Pil/Slash is not translated into English, but well-known to BL fans regardless of its current unavailability in the West. All the characters in this game fit into the switch category, taking both seme and uke roles. 

Parade's No, Thank You!!! and Room no.9 take place in the same timeline, though the games can be played independently of one another. Protagonists Haru and Daichi are exclusively seme characters, with No, Thank You!!! offering multiple love interests and Room no.9 concentrating solely on Daichi's friend Seiji as the object of desire. One of the game's merchandising items is a pillowcase of Seiji designed for the owner to penetrate it.

Lkyt, also from Parade, is a darkly apocalyptic samurai-style visual novel with little in the way of sweet romance, but the bonds between the characters are still meaningful and heartfelt. Protagonist Tasuku, despite being younger than any of the love interests, takes the penetrative role in all sex scenes in the game. 

Togainu no Chi - Lost Blood - fits into the switch-protagonist category, as protagonist Akira is the penetrated character in all but one of the routes. This route, for the character Rin, is unique among Nitro+Chiral's titles in allowing the player character to take the seme role in sex. 

Seiyuu Danshi!, from English-language publisher MeYaoi Games, has a high level of interactivity in the sex scene portions of the game and allows the player to set many variables, including which position each of the participants take.

This is obviously only the smallest sliver of Boys Love games with seme protagonists, but hopefully it's a good starting place!