There are a lot of possibilities, which have already been named, but I can't think of anything that
automatically equals suicidal ideation--this is an uncertain variable.
Alcohol definitely does not go well with depression. I've known more than one person who goes from depressed to suicidal when drinking.
Lariam is a really interesting idea, but as has been said, it's not surefire. Most people do not experience extreme symptoms--but some do go totally batshit insane. I've been on it a number of times and only once experienced anything weird (intense nightmares, and who knows if that was the Lariam or not, as I go through periods of those things anyway).
There are
a lot of drugs, for all sorts of medical conditions, that are reputed to cause suicidal thoughts in a very small number of people...Accutane (for severe/intractable acne), Tamiflu (for the flu), Strattera (for ADHD), etc. But of course, there are tons of people that take these drugs without such effects. (I was on Accutane more than once, and while there were a lot of unpleasant physical effects, I didn't experience any psychiatric problems.)
And of course you can play with any number of hallucinogens or recreational drugs etc. -- things that generally make people crazypants. Meth, LSD, bath salts, yanno. The classics.