There are literally thousands of different deities out there in the Universe, and which ones you choose to honor will often depend significantly upon what pantheon your spiritual path follows. However, many modern Pagans and Wiccans describe themselves as eclectic, which means they may honor a god of one tradition beside a goddess of another. In some cases, we may choose to ask a deity for assistance in a magical working or in problem solving. Regardless, at some point, you're going to have to sit and sort them all out. If you don't have a specific, written tradition, then how do you know which gods to call upon?
A good way to look at it is to figure out which deity of your pantheon would be interested in your purpose. In other words, what gods might take the time to look into your situation? This is where the concept of appropriate worship comes in handy -- if you can't take the time to get to know the deities of your path, then you probably shouldn't be asking them for favors. So first, figure out your goal. Are you doing a working regarding home and domesticity? Then don't call upon some masculine power deity. What if you're celebrating the end of the harvest season, and the dying of the earth? Then you shouldn't be offering milk and flowers to a spring goddess.
Although this is certainly not a comprehensive list of all the gods and their domains, it may help you a bit to get an idea of who is out there, and what sorts of things they may be able to help you with:
For assistance relating to skills, crafts, or handiwork, call upon the Celtic smith god, Lugh. Many other pantheons have forge and craftsmanship gods as well.
When it comes to matters of discord and upsetting the balance of things, some people choose to to check in with Loki, the Norse prankster god. However, it's generally recommended that you don't do this unless you're a devotee of Loki in the first place - you may end up getting more than you bargained for.
If you're doing a working related to destruction, the Celtic war goddess the Morrighan may assist you, but don't trifle with her lightly. A safer bet might be working with Demeter, the Dark Mother of the harvest season.
When you celebrate the fall harvest, you may want to take time to honor Herne, the god of the wild hunt, or Osiris, who is often connected with grain and the harvest. Demeter and her daughter, Persephone, are typically connected with the waning part of the year. Pomona is associated with fruit orchards and the bounty of trees in fall. There are also a number of other harvest gods and gods of the vine who may be interested in what you're doing.
When it comes to fertility, there are plenty of deities out there to ask for assistance. Consider Cernunnos, the wild stag of the forest, or Freya, a goddess of sexual power and energy. If you follow a Roman-based path, try honoring Bona Dea. There are a number of other fertility gods out there as well, each with their own specific domain.
Home and Marriage
Love and Lust
Aphrodite has long been associated with love and beauty, and so has her counterpart, Venus. Likewise, Eros and Cupid are considered representative of masculine lust. Priapus is a god of raw sexuality, including sexual violence.