Here are top-rated Shopify apps that merchants commonly use to raise average order value (AOV). For each I note what it does, where it’s strongest, and a quick rating/pricing note.

• ReConvert — Upsell & Cross Sell
  What it does: Post‑purchase (thank‑you page) funnels, A/B testing, product recommendations and “order bump” offers to capture extra revenue after checkout. Best for easy post‑purchase funnels and thank‑you page customization.
  Rating/pricing: Highly rated on the Shopify App Store (≈4.9★); tiered plans with a low-entry price and free trial. (apps.shopify.com)

• One Click Upsell — Zipify OCU
  What it does: Robust one‑click pre‑ and post‑purchase upsell funnels and offer pages (designed to add items with minimal friction). Best for stores focused on funnel optimization and measurable uplifts in AOV.
  Rating/pricing: Top‑rated (≈4.8★) with fee tiers that scale; free trial available. (apps.shopify.com, zipify.com)

• BOLD Upsell (Bold Commerce)
  What it does: Pre‑checkout and cart upsells, cross‑sells, BOGO and targeted offers across the customer journey. Good for merchants who want advanced targeting and analytics.
  Rating/pricing: Well‑regarded (≈4.5★); commercial pricing with several plan levels. (apps.shopify.com, mageplaza.com)

• Bundler — Product Bundles
  What it does: Build fixed/mix‑and‑match bundles, quantity breaks and volume discounts to encourage larger purchases. Best when your product mix benefits from multi‑item purchases.
  Rating/pricing: Very high rating (≈4.9★); free tier + inexpensive premium plans. (apps.shopify.com)

• Frequently Bought Together (Code Black Belt)
  What it does: Amazon‑style “frequently bought together” recommendations with one‑click bundle buying and AI/manual suggestion options. Great for accessory & complementary product upsells.
  Rating/pricing: Highly rated (≈4.9★); paid plans with a free trial. (apps.shopify.com, web.codeblackbelt.com)

• Wiser — AI Upsell & Cross Sell (Recommended Products)
  What it does: AI‑driven recommendations (frequently bought together, related products), cart drawer upsells, post‑purchase offers and analytics. Good choice if you want strong personalization across many touchpoints.
  Rating/pricing: Excellent ratings (≈5.0★ in the Store); plans start affordably and scale with volume. (apps.shopify.com)

• Honeycomb Upsell & Cross Sell (Conversion Bear)
  What it does: Funnels for product page, cart and post‑purchase upsells with templates and split tests. Best for merchants who want a simple funnel builder and clean UI.
  Rating/pricing: High rating (~4.7★); free plan + paid tiers for higher funnel volumes. (apps.shopify.com)

• Selleasy — Upsell & Cross Sell
  What it does: “Frequently bought together”, cart upsells, add‑ons and post‑purchase offers that are easy to set up without dev work. Good entry‑level app with strong merchant reviews.
  Rating/pricing: Very highly rated (≈4.9★); free tier + low‑cost plans. (apps.shopify.com)

Quick selection tips

• Match app to strategy: use bundles/quantity apps (Bundler) for pack/volume increases; recommendation engines or “frequently bought together” (Wiser, Code Black Belt) for complementary-product AOV; one‑click upsell funnels (Zipify, ReConvert, Honeycomb) for post‑checkout revenue. (burstcommerce.com, apps.shopify.com)
• Test and measure: run A/B tests, track AOV lift vs. cost of the app, and monitor mobile UX impact. Most apps offer trials—use them to measure incremental revenue. (apps.shopify.com)

If you want, I can narrow these to “best for small stores on a budget,” “best for Shopify Plus,” or make a 1‑page comparison matrix with pricing and exact feature differences.