In the book direct mention is only made of Hand Flamers and Rocket Launchers which are occasionally loaded with nuclear warheads, but are we meant to assume that the ape suits do or do not have a "Primary" such as a rifle? Cover art from various editions seems to go back and forth. (sometimes the MI have rifles, but in the original magazine cover they have recoiless rifle looking launchers and the first edition novel they have flametrowers)
In addition to the hand flamer and the rocket launcher, at one point in the first drop Rico uses his "heavy flamer" to burn a hole in a wall. But mostly Rico specifically doesn't talk about their weapons:
[...] what can be done with really modern weapons and how to do it and how to service and maintain the equipment -- simulated nuclear weapons and infantry rockets and various sorts of gas and poison and incendiary and demolition. As well as other things maybe best not discussed.
Eventually we graduated.
I can see that I've left out almost everything. Not a word about most of our weapons, [...]
He does mention that in close quarters they need to use "short-range selective weapons" to not put their squad-mates at risk, but doesn't specify what those are. Neither are "heavy weapons" or "special weapons" defined.
In training they use obsolete rifles with solid slugs as practice for any other type of aimed weapon, but again, no descriptions.
In summary, it's almost definite that they have other weapons (flamers aren't selective, and don't count as aimed weapons either) but we're not given any clues what they do have.