Aikido is an excellent martial art for self defence, incorporating a wide variety of effective techniques, including many throws, joint locks, pins, chokes, and strikes.
Unlike many arts, which favour learning patterns, kata and forms over performing techniques on a partner; Aikido from the outset encourages techniques to be performed on a training partner. Typically this involves taking it in turns to play the roles of the attacker and defender, where the attacker (Uke) will attack with a specific attack, whilst the defender (Tori) will drill a specific technique of defence.
Working with a training partner in this manner, means students gain experience of being attacked in a safe environment, whilst being able to practice their defence. This benefit is instantly appreciated by students as the techniques and distances involved always need to be adjusted to account for the relative size differences between training partners.
In addition the attacker, benefits by mastering the breakfall. Learning breakfalls and the art of Ukemi, is an essential part of Aikido, and possibly the most valuable self defence skill of all, as it can save you from harm in a wide variety of violent and non-violent situations.