A conditional particle meaning 'if' or 'when/after' (if/when X happens then…).
雨が降ったら、試合は中止です。
If it rains, the game will be canceled.
家に着いたら電話して。
Call me when you arrive home.
時間があったら日本へ行きたい。
If I have time, I'd like to go to Japan.
Colloquial topical marker (often ～ったら) expressing mild scorn, annoyance, or surprise about the topic (roughly 'as for X...').
彼ったら、また約束を忘れた。
That guy forgot his promise again.
子供ったら、ほんとにいたずらばかりする。
Kids really only get into mischief.
母ったら、心配しすぎだよ。
Mom, you're worrying too much.
Casual sentence-ending suggestion meaning 'why don't you ...' or 'how about ...'.
このケーキ、食べたら？
Why don't you eat this cake?
先に行ったら？
Why don't you go ahead?
それ、試してみたら？
Why don't you try that?
Colloquial sentence-ending emphatic expression (often ～ったら) used to insist or emphasize what was said ('I tell you!', 'I said so!').
知らないったら！
I told you I don't know!
もう、やめるったら！
I said I'm quitting!
A colloquial vocative/exclamatory use (often ～ったら) used to call or scold someone with frustration or exasperation.
おい、田中ったら、ちゃんと聞いてるのか？
Hey, Tanaka — are you listening properly?
おまえったら、また忘れたのか。
You again — did you forget it again?