Everyone will have their favourite, but it's always useful to remember that every body is different so everyone can't like everything equally. Do you want it to be a surprise, or are you open to browsing with her? Having her input from the get-go can save a lot of time and money. 🙂
Bullets can be a good starter toy. They're small and discreet enough to be used both alone and together, and are good for precision stimulation. Mrs Chimp prefers the lower frequency (rumbly) toys, as opposed to the higher frequency (buzzy) ones as the buzzy ones can leave her feeling numb. We've found that the rechargeable toys are more likely to be rumbly, but the reviews can tell give you a lot of good info about each specific toy. The forum top two bullets always seem to be the We-Vibe Tango and the Desire Bullet (with the Mantric Bullet being a close ish third):
Tango https://www.lovehoney.co.uk/product.cfm?p=30320
Desire https://www.lovehoney.co.uk/product.cfm?p=36366
Mantric https://www.lovehoney.co.uk/product.cfm?p=39046
Wands are another popular clitoral toy shape. More broad stimulation than the bullet shape, and they range from little mini ones to the bigger mains-powered one the size of your forearm. 🙂 Personally we like ours somewhere in the middle. Mrs Chimp's favourits are the Mantric and Desire wands:
Mantric Wand https://www.lovehoney.co.uk/product.cfm?p=37966
Desire Wand https://www.lovehoney.co.uk/product.cfm?p=40341
Suction toys like the Womanizer are well worth a look. They work in a completely different way to regular vibrators, and the stimulation can be pretty intense. 🙂 For some they're a real epiphany, but (like all toys) there are no guarantees, and the expense might make you think twice before buying one on a whim.