The cutie mark, an almost always important part of a pony's life. It shows what they are good at, which skills they exceed in. Your characters cutie mark (even if it's been torn off) affects some things about your pony. It can range from anything from attribute bonuses, skill increase or access to a new ability. Sometimes you need a certain cutie mark to be able to access certain things. For example, a unicorn with a medial cutie mark will have a natural talent for spells within the healing school, average for entertainment spells but difficult with battle spells. Some schools are related to each other, and same goes for cutie marks. For example: If you have an apple cutie mark, you could still with ease handle pears. Not as good as apples, but you'd have a knack for it. Likewise it is with spells. Anything that branch together, you'll have partial bonus from your cutie mark on utilising. More about spells on the spell chapter however.
When it comes to cutie marks. You are pretty much free to pick whatever the hell you want and take a bonus that makes at least a bit sense. Like with virtues, if you want a "big bonus" from your cutie mark, you'll have to take a flaw or backlash from it as well. However, the marks are allot more versatile then your virtue, skills or even your attributes as it can cover pretty much anything. Want more luck? Have a clover cutie mark. Want to be better at rifles? Have a rifle cutie mark? Want to be a prostitute? Have a... I'm honestly a bit unsure about this one... but the point being: You can pick about anything as said, just try to have it makes at least a little sense. Like, a cutie mark of a narwhal giving +5 to your gambling, pilot or doctor skill wouldn't really make any sense essentially.
If you're wondering exactly how "strong"a cutie mark would be, follow this simple guide: When it comes to attributes, +1 or possibly +2 should be more then enough as a bonus. When it comes to skills, ~5-10 would be sufficient. Depending on what type it is, most combat ones would get +5, while many social or "etc" would get +10. Or simply make you trained in a skill. (basically, increase your "known skills" by one.) However, if you choose a skill as your cutie mark, also increase the die you roll to increase by 1 size, as well as a +5 to your confirmation roll if you get to increase your skill. And when it comes to "other tasks" your cutie mark might do, you can simply invent some, such as "once per encounter, take half damage from an attack". So basically, they can be talents to. However, at most a rank 2 talent (and then the rank 1 is not included). Also, a word of advice: seeing how a cutie mark can tell allot about somepony, It is often a good way to notice/be noticed what kind of quirk/talent others/you posses. (ex: pony with a soil/vegetable mark is likely to be assumed to be a farmer)
Also, a word of advice: seeing how a cutie mark can tell allot about somepony, It is often a good way to notice/be noticed what kind of quirk/talent others/you posses. (ex: pony with a soil/vegetable mark is likely to be assumed to be a farmer)