Vec<T>: When you need a dynamic array-like structure, with random indexing by usize, and efficient appending at the end.String: For owned, mutable text data.HashMap<K, V>: For fast lookups by arbitrary keys, remembering to use std::collections::HashMap.BTreeMap<K, V>: For sorted key-value storage and O(log n) complexity.HashSet<T> and BTreeSet<T>: For maintaining unique items.VecDeque<T>: For efficient insertion/removal at both ends.LinkedList<T>: For specific insertion/removal patterns where linked-list semantics are necessary.